Clocking and Timing

This chapter explains how to configure timing ports on the Cisco ASR 920 Series Router.
• Clocking and Timing Restrictions, on page 1
• Clocking and Timing Overview, on page 3
• Configuring Clocking and Timing, on page 14
• Verifying the Configuration, on page 45
• Troubleshooting, on page 45
• Configuration Examples, on page 47

Clocking and Timing Restrictions

The following clocking and timing restrictions apply to the Cisco ASR 920 Series Router:
• Do not configure GNSS in high accuracy operating mode, when Cisco ASR-920-12SZ-A or Cisco
ASR-920-12SZ-D router is configured as Precision Time Protocol (PTP) master.
• You can configure only a single clocking input source within each group of eight ports (0–7 and 8–15)
on the T1/E1 interface module using the network-clock input-source command.
• Multicast timing is not supported.
• Precision Time Protocol (PTP) is supported only on loopback interfaces, layer 2 interfaces, and BDI
interfaces. It is not supported on Layer 3 interfaces.
• Out-of-band clocking and the recovered-clock command are not supported.
• Synchronous Ethernet clock sources are not supported with PTP. Conversely, PTP clock sources are not
supported with synchronous Ethernet except when configured as hybrid clock. However, you can use
hybrid clocking to allow the router to obtain frequency using Synchronous Ethernet, and phase using
PTP.
• Time of Day (ToD) and 1 Pulse per Second (1PPS) input is not supported when the router is in boundary
clock mode.
• On Cisco ASR 920 Series Router (ASR-920-12CZ-A, ASR-920-12CZ-D, ASR-920-4SZ-A, and
ASR-920-4SZ-D), 1 PPS is only available through ToD port. To provide both ToD and 1 PPS signal on
the same port you must use a special Y-cable.

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Clocking and Timing Restrictions

Note The Cisco ASR-920-24SZ-M and ASR-920-24TZ-M do not have a ToD port,
BITS port or a 1pps SMB port.

• Cisco ASR 920 Series Router (ASR-920-12CZ-A, ASR-920-12CZ-D, ASR-920-4SZ-A, ASR-920-4SZ-D,

ASR-920-24SZ-M, ASR-920-24TZ-M), supports only BITS port and not 10 M input.

Note Fixed Cisco ASR-920-24SZ-IM, ASR-920-24SZ-M, ASR-920-24TZ-M

Aggregation Services Routers cannot take any external input and cannot give out
any external output.

• Multiple ToD clock sources are not supported.

• PTP redundancy is supported only on unicast negotiation mode; you can configure up to three master
clocks in redundancy mode.
• In order to configure time of day input, you must configure both an input 10 Mhz and an input 1 PPS
source.
• PTP over IPv6 is not supported.
• When PTP is configured on Cisco ASR-920-24SZ-IM Router, changing the configuration mode from
LAN to WAN or WAN to LAN is not supported for following IMs:
• 2x10G
• 8x1G_1x10G_SFP
• 8x1G_1x10G_CU

• PTP functionality is restricted by license type.

The table below summarizes the PTP functionalities that are available, by license type:

Table 1: PTP Functions Supported by Different Licenses

License PTP Support

Metro Services Not supported

Metro IP Service Ordinary Slave Clock

Metro Aggregation Service Ordinary Slave Clock

Metro IP Service + IEEE 1588-2008 BC/MC All PTP functionality including boundary and master
clock

Metro Aggregation Service + IEEE 1588-2008 All PTP functionality including boundary and master
BC/MC clock

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Clocking and Timing Overview

Note If you install the IEEE 1588-2008 BC/MC license, you must reload the router to use the full PTP functionality.

• End-to-end Transparent Clock is not supported for PTP over Ethernet.

• G.8265.1 telecom profiles are not supported with PTP over Ethernet.
• The Cisco ASR 920 Series Router do not support a mix of IPv4 and Ethernet clock ports when acting as
a transparent clock or boundary clock.

The following restrictions apply when configuring synchronous Ethernet SSM and ESMC:
• To use the network-clock synchronization ssm option command, ensure that the router configuration
does not include the following:
• Input clock source
• Network clock quality level
• Network clock source quality source (synchronous Ethernet interfaces)

• The network-clock synchronization ssm option command must be compatible with the network-clock
eec command in the configuration.
• To use the network-clock synchronization ssm option command, ensure that there is not a network
clocking configuration applied to synchronous Ethernet interfaces, BITS interfaces, and timing port
interfaces.
• We recommended that you do not configure multiple input sources with the same priority as this impacts
the TSM (Switching message delay).
• You can configure a maximum of 4 clock sources on interface modules, with a maximum of 2 per interface
module. This limitation applies to both synchronous Ethernet and TDM interfaces.
• The network-clock input-interface ptp domain command is not supported.
• To shift from non hybrid clock configuration to hybrid clock configuration, you must first unconfigure
PTP, unconfigure netsync, reconfigure netsync and configure hybrid PTP.

Clocking and Timing Overview

The Cisco ASR 920 Series Router have the following timing ports:
• 1 PPS Input/Output
• 10 Mhz Input/Output
• ToD
• Building Integrated Timing Supply (BITS)
You can use the timing ports on the Cisco ASR 920 Series Router to perform the following tasks:
• Provide or receive 1 PPS messages
• Provide or receive time of day (ToD) messages
• Provide output clocking at 10 Mhz, 2.048 Mhz, and 1.544 Mhz (Cisco ASR-920-24SZ-IM Router)

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Understanding PTP

• Receive input clocking at 10 Mhz, 2.048 Mhz, and 1.544 Mhz (Cisco ASR-920-24SZ-IM Router)
SyncE is supported in both LAN and WAN mode on a 10 Gigabit Ethernet interface.

Understanding PTP
The Precision Time Protocol (PTP), as defined in the IEEE 1588 standard, synchronizes with nanosecond
accuracy the real-time clocks of the devices in a network. The clocks in are organized into a master-member
hierarchy. PTP identifies the switch port that is connected to a device with the most precise clock. This clock
is referred to as the master clock. All the other devices on the network synchronize their clocks with the master
and are referred to as members. Constantly exchanged timing messages ensure continued synchronization.
PTP is particularly useful for industrial automation systems and process control networks, where motion and
precision control of instrumentation and test equipment are important.

Table 2: Nodes within a PTP Network

Network Element Description

Grandmaster (GM) A network device physically attached to the primary time source. All clocks are synchronized to the
grandmaster clock.

Ordinary Clock (OC) An ordinary clock is a 1588 clock with a single PTP port that can operate in one of the following modes:
• Master mode—Distributes timing information over the network to one or more slave clocks, thus
allowing the slave to synchronize its clock to the master.
• Slave mode—Synchronizes its clock to a master clock. You can enable the slave mode on up to two
interfaces simultaneously in order to connect to two different master clocks.

Boundary Clock (BC) The device participates in selecting the best master clock and can act as the master clock if no better clocks
are detected.
Boundary clock starts its own PTP session with a number of downstream slaves. The boundary clock
mitigates the number of network hops and results in packet delay variations in the packet network between
the Grand Master and Slave.

Transparent Clock (TC) A transparent clock is a device or a switch that calculates the time it requires to forward traffic and updates
the PTP time correction field to account for the delay, making the device transparent in terms of time
calculations.

Telecom Profiles
Release 3.8 introduces support for telecom profiles, which allow you to configure a clock to use the G.8265.1
recommendations for establishing PTP sessions, determining the best master clock, handling SSM, and
mapping PTP classes. For information about how to configure telecom profiles, see Configuring Clocking
and Timing.
Effective Cisco IOS-XE Release 3.18, the G.8275.1 telecom profile is also supported on the Cisco ASR920
Series Routers (Cisco ASR-920-12CZ-A/D, ASR-920-4SZ-A/D, Cisco ASR 920-10SZ-PD and Cisco
ASR-920-24SZ-IM, ASR-920-24SZ-M, ASR-920-24TZ-M). For more information, see G.8275.1 Telecom
Profile.

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PTP Redundancy

PTP Redundancy
PTP redundancy is an implementation on different clock nodes. This helps the PTP slave clock node achieve
the following:
• Interact with multiple master ports such as grand master clocks and boundary clock nodes.
• Open PTP sessions.
• Select the best master from the existing list of masters (referred to as the primary PTP master port or
primary clock source).
• Switch to the next best master available in case the primary master fails, or the connectivity to the primary
master fails.

Note BMCA can also be triggered if clock class of the newly-added master is better. This is true for both, normal
PTP as well as PTP with hybrid.

Note The Cisco ASR 920 Series Router supports unicast-based timing as specified in the 1588-2008 standard.

For instructions on how to configure PTP redundancy, see Configuring PTP Redundancy, on page 32.

PTP Redundancy Using Hop-By-Hop Topology Design

Real world deployments for IEEE-1588v2 for mobile backhaul requires the network elements to provide
synchronization and phase accuracy over IP or MPLS networks along with redundancy.
In a ring topology, a ring of PTP boundary clock nodes are provisioned such that each boundary clock node
provides synchronization to a number of PTP slaves connected to it. Each such ring includes at least two PTP
masters with a PRC traceable clock.
However, with this topology the following issues may occur:
• Node asymmetry and delay variation—In a ring topology, each boundary clock uses the same master,
and the PTP traffic is forwarded through intermediate boundary clock nodes. As intermediate nodes do
not correct the timestamps, variable delay and asymmetry for PTP are introduced based on the other
traffic passing through such nodes, thereby leading to incorrect results.
• Clock redundancy—Clock redundancy provides redundant network path when a node goes down. In a
ring topology with PTP, for each unicast PTP solution, the roles of each node is configured. The PTP
clock path may not be able to reverse without causing timing loops in the ring.

No On-Path Support Topology

The topology (see the figure below ) describes a ring with no on-path support. S1 to S5 are the boundary
clocks that use the same master clocks. GM1 and GM2 are the grandmaster clocks. In this design, the following
issues are observed:
• Timestamps are not corrected by the intermediate nodes.
• Difficult to configure the reverse clocking path for redundancy.
• Formation of timings loops.

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Hop-By-Hop Topology in a PTP Ring

Figure 1: Deployment in a Ring - No On-Path Support with IPv4

Table 3: PTP Ring Topology—No On-Path Support

Clock Nodes Behavior in the PTP Ring

GM1 Grandmaster Clock

GM2 Grandmaster Clock

S1 Masters: M1 (1st), M2 (2nd)

S2 Masters: M1 (1st), M2 (2nd)

S3 Masters: M1 (1st), M2 (2nd)

S4 Masters: M2 (1st), M1 (2nd)

S5 Masters: M2 (1st), M1 (2nd)

A solution to the above issue is addressed by using Hop-by-Hop topology configuration.

Hop-By-Hop Topology in a PTP Ring

PTP Ring topology is designed by using Hop-By-Hop configuration of PTP boundary clocks. In this topology,
each BC selects its adjacent nodes as PTP masters, instead of using the same GM as the PTP master. These
PTP BC masters are traceable to the GM in the network. Timing loop are not formed between adjacent BC
nodes. The hot Standby BMCA configuration is used for switching to next the best master during failure.

Prerequisites
• PTP boundary clock configuration is required on all clock nodes in the ring, except the master clock
nodes (GM), which provide the clock timing to ring. In the above example nodes S1—S5 must be
configured as BC.
• The master clock (GM1 and GM2 in the above figure ) nodes in the ring can be either a OC master or
BC master.

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Restrictions

• Instead of each BC using same the GM as a PTP master, each BC selects its adjacent nodes as PTP
masters. These PTP BC-masters are traceable to the GM in the network.
• Boundary clock nodes must be configured with the single-hop keyword in the PTP configuration to
ensure that a PTP node can communicate with it’s adjacent nodes only.

Restrictions
• Timing loops should not exist in the topology. For example, if for a node there are two paths to get the
same clock back, then the topology is not valid. Consider the following topology and configuration.

The paths with double arrows (>>) are the currently active clock paths and paths with single arrow (>) are
redundant clock path. This configuration results in a timing loop if the link between the BC-1 and GM fails.

• In a BC configuration, the same loopback interface should never be used for both master and slave port
configuration.
• Single-hop keyword is not supported for PTP over MPLS with explicit null configuration. The Single-hop
keyword is not supported when PTP packets are sent out with a MPLS tag.

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On-Path Support Topology Scenario

On-Path Support Topology Scenario

Consider the topology as shown in the figure in the section No On-Path Support Topology .
Figure 2: PTP Ring Topology—On-Path Support

Table 4: PTP Ring Topology—On-Path Support

Clock Node Behavior in the PTP Ring

GM1 Grandmaster Clock

GM2 Grandmaster Clock

BC1 Masters: M1 (1st), BC2 (2nd)

Slaves: BC2

BC2 Masters: BC1(1st), BC3 (2nd)

Slaves: BC1, BC3

BC3 Masters: BC2 (1st), BC4 (2nd)

Slaves: BC2, BC4

BC4 Masters: BC5 (1st), BC3 (2nd)

Slaves: BC3, BC5

BC5 Masters: M2(1st), BC4 (2nd)

Slaves: BC4

Now consider there is a failure between BC1 and BC2 (see the figure below ). In this case, the BC2 cannot
communicate with GM1. Node BC2 receives the clock from BC3, which in turn receives the clock from GM2.

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On-Path Support Topology Scenario

Figure 3: Deployment in a Ring—On-Path Support (Failure)

Table 5: PTP Ring Topology—On-Path Support (Failure)

1
Clock Node Behavior in the PTP Ring

GM1 Grandmaster Clock

GM2 Grandmaster Clock

BC1 Masters: M1 (1st), BC2 (2nd)

Slaves: BC2

BC2 Masters: BC1(1st), BC3 (2nd)

Slaves: BC1, BC3

BC3 Masters: BC2 (1st), BC4 (2nd)

Slaves: BC2, BC4

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Configuration Example

1
Clock Node Behavior in the PTP Ring

BC4 Masters: BC5 (1st), BC3 (2nd)

Slaves: BC3, BC5

BC5 Masters: M2(1st), BC4 (2nd)

Slaves: BC4
1
Red indicates that GM is not traceable and there is no path to the slave.

Configuration Example
PTP Ring boundary clocks must be configured with single-hop keyword in PTP configuration. The PTP node
can communicate with its adjacent nodes only. This is required for PTP hop-by-hop ring topology.

ptp clock boundary domain 0

clock-port bcslave1 slave
transport ipv4 unicast interface Lo0 negotiation single-hop
clock source 1.1.1.1
clock source 2.2.2.2 1
clock-port bcmaster1 master
transport ipv4 unicast interface Lo1 negotiation single-hop
.
.

Note The single-hop keyword is not supported for PTP over MPLS with explicit NULL configurations. The
single-hop keyword is not supported when PTP packets are sent out with a MPLS tag.

For information on configuring PTP redundancy, see Configuring PTP Redundancy .

Best Master Clock Algorithm

Effective Cisco IOS-XE Release 3.15.0S, Best Master Clock Algorithm (BMCA) is supported on the Cisco
ASR 920 Series Routers.
BMCA is used to select the master clock on each link, and ultimately, select the grandmaster clock for the
entire Precision Time Protocol (PTP) domain. BCMA runs locally on each port of the ordinary and boundary
clocks, and selects the best clock.
The best master clock is selected based on the following parameters:
• Priority—User-configurable value ranging from 0 to 255; lower value takes precedence
• Clock Class—Defines the traceability of time or frequency from the grandmaster clock
• Alarm Status—Defines the alarm status of a clock; lower value takes precedence
By changing the user-configurable values, network administrators can influence the way the grandmaster
clock is selected.
BMCA provides the mechanism that allows all PTP clocks to dynamically select the best master clock
(grandmaster) in an administration-free, fault-tolerant way, especially when the grandmaster clocks changes.
For information on configuring BMCA, see Configuring Clocking and Timing, on page 14.

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Hybrid BMCA

Hybrid BMCA
In hybrid BMCA implementation, the phase is derived from a PTP source and frequency is derived from a
physical lock source. More than one master clock is configured in this model and the best master is selected.
If the physical clock does down, then PTP is affected.

Configuration Example: Hybrid BMCA on Ordinary Clock

ptp clock ordinary domain 0 hybrid

clock-port SLAVE slave
transport ipv4 unicast interface Lo0 negotiation
clock source 133.133.133.133
clock source 144.144.144.144 1
clock source 155.155.155.155 2

Network-clock input-source 10 interface gigabitEthernet 0/4

Configuration Example: Hybrid BMCA on Boundary Clock

ptp clock boundary domain 0 hybrid

clock-port SLAVE slave
transport ipv4 unicast interface Lo0 negotiation
clock source 133.133.133.133
clock source 144.144.144.144 1
clock source 155.155.155.155 2
clock-port MASTER master
transport ipv4 unicast interface Lo1 negotiation

Network-clock input-source 10 interface gigabitEthernet 0/4

Hybrid Clocking
The Cisco ASR 920 Series Router support a hybrid clocking mode that uses clock frequency obtained from
the synchronous Ethernet port while using the phase (ToD or 1 PPS) obtained using PTP. The combination
of using physical source for frequency and PTP for time and phase improves the performance as opposed to
using only PTP.

Note When configuring a hybrid clock, ensure that the frequency and phase sources are traceable to the same master
clock.

For more information on how to configure hybrid clocking, see Configuring a Transparent Clock, on page
24.

Transparent Clocking
A transparent clock is a network device such as a switch that calculates the time it requires to forward traffic
and updates the PTP time correction field to account for the delay, making the device transparent in terms of
timing calculations. The transparent clock ports have no state because the transparent clock does not need to
synchronize to the grandmaster clock.
There are two kinds of transparent clocks:
• End-to-end transparent clock—Measures the residence time of a PTP message and accumulates the times
in the correction field of the PTP message or an associated follow-up message.

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Time of Day (TOD)

• Peer-to-peer transparent clock— Measures the residence time of a PTP message and computes the link
delay between each port and a similarly equipped port on another node that shares the link. For a packet,
this incoming link delay is added to the residence time in the correction field of the PTP message or an
associated follow-up message.

Note The Cisco ASR 920 Series Router does not currently support peer-to-peer transparent clock mode.

For information on how to configure the Cisco ASR 920 Series Router as a transparent clock, see Configuring
a Transparent Clock, on page 24.

Time of Day (TOD)

You can use the time of day (ToD) and 1PPS ports on the Cisco ASR 920 Series Router to exchange ToD
clocking. In master mode, the router can receive time of day (ToD) clocking from an external GPS unit; the
router requires a ToD, 1PPS, and 10MHZ connection to the GPS unit.
In slave mode, the router can recover ToD from a PTP session and repeat the signal on ToD and 1PPS interfaces.
For instructions on how to configure ToD on the Cisco ASR 920 Series Router, see the Configuring a Master
Ordinary Clock, on page 14 and Configuring a Slave Ordinary Clock, on page 19.

Synchronizing the System Clock to Time of Day

You can set the router’s system time to synchronize with the time of day retrieved from an external GPS
device. For information on how to configure this feature, see Synchronizing the System Time to a Time-of-Day
Source, on page 36.

Timing Port Specifications

The following sections provide specifications for the timing ports on the Cisco ASR 920 Series Router.

BITS Framing Support

The table below lists the supported framing modes for a BITS port.

Table 6: Framing Modes for a BITS Port on a Cisco ASR 920 Series Router

BITS or SSU Port Support Matrix Framing Modes Supported SSM or QL Support Tx Rx
Port Port

T1 T1 ESF Yes Yes Yes

T1 T1 SF No Yes Yes

E1 E1 CRC4 Yes Yes Yes

E1 E1 FAS No Yes Yes

2048 kHz 2048 kHz No Yes Yes

The BITS port behaves similarly to the T1/E1 ports on the T1/E1 interface module.

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Understanding Synchronous Ethernet ESMC and SSM

Understanding Synchronous Ethernet ESMC and SSM

Synchronous Ethernet incorporates the Synchronization Status Message (SSM) used in Synchronous Optical
Networking (SONET) and Synchronous Digital Hierarchy (SDH) networks. While SONET and SDH transmit
the SSM in a fixed location within the frame, Ethernet Synchronization Message Channel (ESMC) transmits
the SSM using a protocol: the IEEE 802.3 Organization-Specific Slow Protocol (OSSP) standard.
The ESMC carries a Quality Level (QL) value identifying the clock quality of a given synchronous Ethernet
timing source. Clock quality values help a synchronous Ethernet node derive timing from the most reliable
source and prevent timing loops.
When configured to use synchronous Ethernet, the Cisco ASR 920 Series Router synchronizes to the best
available clock source. If no better clock sources are available, the router remains synchronized to the current
clock source.
The router supports two clock selection modes: QL-enabled and QL-disabled. Each mode uses different criteria
to select the best available clock source.
For more information about Ethernet ESMC and SSM, seeConfiguring Synchronous Ethernet ESMC and
SSM, on page 38.

Note The router can only operate in one clock selection mode at a time.

Note PTP clock sources are not supported with synchronous Ethernet.

Clock Selection Modes

The Cisco ASR 920 Series Router supports two clock selection modes, which are described in the following
sections.

QL-Enabled Mode
In QL-enabled mode, the router considers the following parameters when selecting a clock source:
• Clock quality level (QL)
• Clock availability
• Priority

QL-Disabled Mode
In QL-disabled mode, the router considers the following parameters when selecting a clock source:
• Clock availability
• Priority

Note You can use override the default clock selection using the commands described in the Specifying a Clock
Source, on page 43 and Disabling a Clock Source, on page 44 sections.

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Managing Clock Selection

Managing Clock Selection

You can manage clock selection by changing the priority of the clock sources; you can also influence clock
selection by modifying modify the following clock properties:
• Hold-Off Time—If a clock source goes down, the router waits for a specific hold-off time before removing
the clock source from the clock selection process. By default, the value of hold-off time is 300 ms.
• Wait to Restore—The amount of time that the router waits before including a newly active synchronous
Ethernet clock source in clock selection. The default value is 300 seconds.
• Force Switch—Forces a switch to a clock source regardless of clock availability or quality.
• Manual Switch—Manually selects a clock source, provided the clock source has a equal or higher quality
level than the current source.
For more information about how to use these features, see Specifying a Clock Source, on page 43 and Disabling
a Clock Source, on page 44 sections.

Configuring Clocking and Timing

The following sections describe how to configure clocking and timing features on the Cisco ASR 920 Series
Router:

Configuring a Master Ordinary Clock

Follow these steps to configure the Cisco ASR 920 Series Router to act as a master ordinary clock.

SUMMARY STEPS
1. enable
2. configure terminal
3. platform ptp 1pps GPS
4. ptp clock ordinary domain domain-number
5. priority1 priorityvalue
6. priority2 priorityvalue
7. utc-offset value leap-second “date time” offset {-1 | 1}
8. input [1pps] {R0 | R1}
9. tod {R0 | R1} {ubx | nmea | cisco | ntp}
10. clock-port port-name {master | slave} [profile {g8265.1}]
11. Do one of the following:
• transport ipv4 unicast interface interface-type interface-number [negotiation]
• transport ethernet unicast [negotiation]
12. exit
13. network-clock synchronization automatic
14. network-clock synchronization mode ql-enabled
15. Use one of the following options:
• network-clock input-source <priority> controller {SONET | wanphy}
• network-clock input-source <priority> external {R0 | R1} [10m | 2m]

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Configuring a Master Ordinary Clock

• network-clock input-source <priority> external {R0 | R1} [2048k | e1 {cas {120ohms | 75ohms |
crc4}}]
• network-clock input-source <priority> external {R0 | R1} [2048k | e1 {crc4 | fas] {120ohms |
75ohms} {linecode {ami | hdb3}}
• network-clock input-source <priority> external {R0 | R1} [t1 {d4 | esf | sf} {linecode {ami | b8zs}}]
• network-clock input-source <priority> interface <type/slot/port>
16. clock destination source-address | mac-address {bridge-domain bridge-domain-id} | interface
interface-name}
17. sync interval interval
18. announce interval interval
19. end

DETAILED STEPS

Command or Action Purpose

Step 1 enable Enables privileged EXEC mode.
Example: • Enter your password if prompted.

Router> enable

Step 2 configure terminal Enters configuration mode.

Example:

Router# configure terminal

Step 3 platform ptp 1pps GPS Enables 1pps SMA port.

Example:
Router(config)#platform ptp 1pps GPS

Step 4 ptp clock ordinary domain domain-number Configures the PTP clock. You can create the following
clock types:
Example:
• ordinary—A 1588 clock with a single PTP port that
Router(config)# ptp clock ordinary domain 0 can operate in Master or Slave mode.
Example:

Router(config-ptp-clk)#

Step 5 priority1 priorityvalue Sets the preference level for a clock. Slave devices use the
priority1 value when selecting a master clock: a lower
Example:
priority1 value indicates a preferred clock. The priority1
value is considered above all other clock attributes.
Router(config-ptp-clk)# priority1 priorityvalue
Valid values are from 0-255. The default value is 128.

Step 6 priority2 priorityvalue Sets a secondary preference level for a clock. Slave devices
use the priority2 value when selecting a master clock: a
Example:
lower priority2 value indicates a preferred clock. The
Router(config-ptp-clk)# priority2 priorityvalue

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Configuring a Master Ordinary Clock

Command or Action Purpose

priority2 value is considered only when the router is unable
to use priority1 and other clock attributes to select a clock.
Valid values are from 0-255. The default value is 128.

Step 7 utc-offset value leap-second “date time” offset {-1 | 1} (Optional) Starting with Cisco IOS-XE Release 3.18SP,
the new utc-offset CLI is used to set the UTC offset value.
Example:
Valid values are from 0-255. The default value is 36.
Router(config-ptp-clk)# utc-offset 45
(Optional) Starting with Cisco IOS-XE Release 3.18.1SP,
leap-second “01-01-2017 00:00:00” offset you can configure the current UTC offset, leap second
1 event date and Offset value (+1 or -1). Leap second
configuration will work only when the frequency source
is locked and ToD was up before.
• “date time”— Leap second effective date in
dd-mm-yyyy hh:mm:ss format.

Step 8 input [1pps] {R0 | R1} Enables Precision Time Protocol input 1PPS using a 1PPS
input port.
Example:
Use R0 or R1 to specify the active RSP slot.
Router(config-ptp-clk)# input 1pps R0

Step 9 tod {R0 | R1} {ubx | nmea | cisco | ntp} Configures the time of day message format used by the
ToD interface.
Example:
Note It is mandatory that when electrical ToD is used,
Router(config-ptp-clk)# tod R0 ntp the utc-offset command is configured before
configuring the tod R0, otherwise there will be
a time difference of approximately 37 seconds
between the master and slave clocks.

Note The ToD port acts as an input port in case of

Master clock and as an output port in case of
Slave clock.

Step 10 clock-port port-name {master | slave} [profile {g8265.1}] Defines a new clock port and sets the port to PTP master
or slave mode; in master mode, the port exchanges timing
Example:
packets with PTP slave devices.
Router(config-ptp-clk)# clock-port Master The profile keyword configures the clock to use the
master G.8265.1 recommendations for establishing PTP sessions,
determining the best master clock, handling SSM, and
Example: mapping PTP classes.
Router(config-ptp-port)# Note Using a telecom profile requires that the clock
have a domain number of 4–23.

Step 11 Do one of the following: Specifies the transport mechanism for clocking traffic; you
can use IPv4 or Ethernet transport.
• transport ipv4 unicast interface interface-type
interface-number [negotiation] The negotiation keyword configures the router to discover
• transport ethernet unicast [negotiation] a PTP master clock from all available PTP clock sources.

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16
 Clocking and Timing
Configuring a Master Ordinary Clock

Command or Action Purpose

Example: Note PTP redundancy is supported only on unicast
negotiation mode.
Router(config-ptp-port)# transport ipv4 unicast
interface loopback 0 negotiation

Step 12 exit Exits clock-port configuration.

Step 13 network-clock synchronization automatic Enables automatic selection of a clock source.

Example: Note This command is mandatory to configure the
leap second command.
Router(config)# network-clock synchronization
automatic Note This command must be configured before any
input source.

Step 14 network-clock synchronization mode ql-enabled Enables automatic selection of a clock source based on
quality level (QL).
Example:
Note This command is disabled by default.
network-clock
Router(config)#
synchronization mode ql-enabled

Step 15 Use one of the following options: • (Optional) To nominate SDH or SONET controller
as network clock input source.
• network-clock input-source <priority> controller
{SONET | wanphy} • (Optional) To nominate 10Mhz port as network clock
• network-clock input-source <priority> external {R0 input source.
| R1} [10m | 2m]
• (Optional) To nominate BITS port as network clock
• network-clock input-source <priority> external {R0
input source in e1 mode.
| R1} [2048k | e1 {cas {120ohms | 75ohms | crc4}}]
• network-clock input-source <priority> external {R0 • (Optional) To nominate BITS port as network clock
| R1} [2048k | e1 {crc4 | fas] {120ohms | 75ohms} input source in e1 mode.
{linecode {ami | hdb3}}
• (Optional) To nominate BITS port as network clock
• network-clock input-source <priority> external {R0
input source in t1 mode.
| R1} [t1 {d4 | esf | sf} {linecode {ami | b8zs}}]
• network-clock input-source <priority> interface • (Optional) To nominate Ethernet interface as network
<type/slot/port> clock input source.
Example:

Router(config)# network-clock input-source 1

external R0 10m

Step 16 clock destination source-address | mac-address Specifies the IP address or MAC address of a clock
{bridge-domain bridge-domain-id} | interface destination when the router is in PTP master mode.
interface-name}
Example:

Router(config-ptp-port)# clock-source 8.8.8.1

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 Clocking and Timing
Configuring a Master Ordinary Clock

Command or Action Purpose

Step 17 sync interval interval Specifies the interval used to send PTP synchronization
messages. The intervals are set using log base 2 values, as
Example:
follows:
Router(config-ptp-port)# sync interval -4 • 1—1 packet every 2 seconds
• 0—1 packet every second
• -1—1 packet every 1/2 second, or 2 packets per
second
• -2—1 packet every 1/4 second, or 4 packets per
second
• -3—1 packet every 1/8 second, or 8 packets per
second
• -4—1 packet every 1/16 seconds, or 16 packets per
second.
• -5—1 packet every 1/32 seconds, or 32 packets per
second.
• -6—1 packet every 1/64 seconds, or 64 packets per
second.
• -7—1 packet every 1/128 seconds, or 128 packets per
second.

Step 18 announce interval interval Specifies the interval for PTP announce messages. The
intervals are set using log base 2 values, as follows:
Example:
• 3—1 packet every 8 seconds
Router(config-ptp-port)# announce interval 2
• 2—1 packet every 4 seconds
• 1—1 packet every 2 seconds
• 0—1 packet every second
• -1—1 packet every 1/2 second, or 2 packets per
second
• -2—1 packet every 1/4 second, or 4 packets per
second
• -3—1 packet every 1/8 second, or 8 packets per
second

Step 19 end Exit configuration mode.

Example:

Router(config-ptp-port)# end

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18
 Clocking and Timing
Configuring a Slave Ordinary Clock

Example
The following example shows that the utc-offset is configured before configuring the ToD to avoid
a delay of 37 seconds between the master and slave clocks:
ptp clock ordinary domain 24

local-priority 1

priority2 128
utc-offset 37
tod R0 cisco
clock-port master-port-1 master profile g8275.1 local-priority 1
transport ethernet multicast interface Gig 0/0/1

Configuring a Slave Ordinary Clock

Follow these steps to configure the Cisco ASR 920 Series Router to act as a slave ordinary clock.

SUMMARY STEPS
1. enable
2. configure terminal
3. ptp clock ordinary domain domain-number [hybrid]
4. output [1pps] {R0 | R1} [offset offset-value] [pulse-width value]
5. tod {R0 | R1} {ubx | nmea | cisco | ntp}
6. clock-port port-name {master | slave} [profile {g8265.1}]
7. Do one of the following:
• transport ipv4 unicast interface interface-type interface-number [negotiation]
•
• transport ethernet unicast [negotiation]
8. clock source source-address | mac-address {bridge-domain bridge-domain-id} | interface
interface-name} [priority]
9. announce timeout value
10. delay-req interval interval
11. end

DETAILED STEPS

Command or Action Purpose

Step 1 enable Enables privileged EXEC mode.
Example: • Enter your password if prompted.

Router> enable

Step 2 configure terminal Enter configuration mode.

Example:

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19
 Clocking and Timing
Configuring a Slave Ordinary Clock

Command or Action Purpose

Router# configure terminal

Step 3 ptp clock ordinary domain domain-number [hybrid] Configures the PTP clock. You can create the following
clock types:
Example:
• ordinary—A 1588 clock with a single PTP port that
Router(config)# ptp clock ordinary domain 0 can operate in Master or Slave mode.

Step 4 output [1pps] {R0 | R1} [offset offset-value] [pulse-width Enables Precision Time Protocol input 1PPS using a 1PPS
value] input port.
Example: Use R0 or R1 to specify the active RSP slot.
Note Effective Cisco IOS XE Everest 16.6.1, on the
Router(config-ptp-clk)# output 1pps R0 offset 200
pulse-width 20 μsec Cisco ASR-920-12SZ-IM router, the 1pps pulse
bandwith can be changed from the default value
of 500 milliseconds to up to 20 microsecond.

Step 5 tod {R0 | R1} {ubx | nmea | cisco | ntp} Configures the time of day message format used by the
ToD interface.
Example:
Note The ToD port acts as an input port in case of
Router(config-ptp-clk)# tod R0 ntp Master clock and as an output port in case of
Slave clock.

Step 6 clock-port port-name {master | slave} [profile {g8265.1}] Sets the clock port to PTP master or slave mode; in slave
mode, the port exchanges timing packets with a PTP master
Example:
clock.
Router(config-ptp-clk)# clock-port Slave slave The profile keyword configures the clock to use the
G.8265.1 recommendations for establishing PTP sessions,
determining the best master clock, handling SSM, and
mapping PTP classes.
Note Using a telecom profile requires that the clock
have a domain number of 4–23.

Step 7 Do one of the following: Specifies the transport mechanism for clocking traffic; you
can use IPv4 or Ethernet transport.
• transport ipv4 unicast interface interface-type
interface-number [negotiation] The negotiation keyword configures the router to discover
• a PTP master clock from all available PTP clock sources.
• transport ethernet unicast [negotiation] Note PTP redundancy is supported only on unicast
Example: negotiation mode.

Router(config-ptp-port)# transport ipv4 unicast

interface loopback 0 negotiation

Step 8 clock source source-address | mac-address Specifies the IP or MAC address of a PTP master clock.
{bridge-domain bridge-domain-id} | interface
interface-name} [priority]
Example:

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20
 Clocking and Timing
Configuring a Boundary Clock

Command or Action Purpose

Router(config-ptp-port)# clock-source 8.8.8.1

Step 9 announce timeout value Specifies the number of PTP announcement intervals
before the session times out. Valid values are 1-10.
Example:

Router(config-ptp-port)# announce timeout 8

Step 10 delay-req interval interval Configures the minimum interval allowed between PTP
delay-request messages when the port is in the master state.
Example:
The intervals are set using log base 2 values, as follows:
Router(config-ptp-port)# delay-req interval 1
• 3—1 packet every 8 seconds
• 2—1 packet every 4 seconds
• 1—1 packet every 2 seconds
• 0—1 packet every second
• -1—1 packet every 1/2 second, or 2 packets per
second
• -2—1 packet every 1/4 second, or 4 packets per
second
• -3—1 packet every 1/8 second, or 8 packets per
second
• -4—1 packet every 1/16 seconds, or 16 packets per
second.
• -5—1 packet every 1/32 seconds, or 32 packets per
second.
• -6—1 packet every 1/64 seconds, or 64 packets per
second.
• -7—1 packet every 1/128 seconds, or 128 packets per
second.

Step 11 end Exit configuration mode.

Example:

Router(config-ptp-port)# end

Configuring a Boundary Clock

Follow these steps to configure the Cisco ASR 920 Series Router to act as a boundary clock.

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21
 Clocking and Timing
Configuring a Boundary Clock

SUMMARY STEPS
1. enable
2. configure terminal
3. ptp clock ordinary domain domain-number
4. time-properties persist value
5. clock-port port-name {master | slave} [profile {g8265.1}]
6. transport ipv4 unicast interface interface-type interface-number [negotiation]
7. clock-source source-address [priority]
8. clock-port port-name {master | slave} [profile {g8265.1}]
9. transport ipv4 unicast interface interface-type interface-number [negotiation]
10. end

DETAILED STEPS

Command or Action Purpose

Step 1 enable Enables privileged EXEC mode.
Example: • Enter your password if prompted.

Router> enable

Step 2 configure terminal Enter configuration mode.

Example:

Router# configure terminal

Step 3 ptp clock ordinary domain domain-number Configures the PTP clock. You can create the following
clock types:
Example:
• ordinary—A 1588 clock with a single PTP port that
Router(config)# ptp clock ordinary domain 0 can operate in Master or Slave mode.

Step 4 time-properties persist value (Optional) Starting with Cisco IOS-XE Release 3.18.1SP,
you can configure time properties holdover time. Valid
Example:
values are from 0 to 10000 seconds.
Router(config-ptp-clk)# time-properties When a master clock is lost, the time properties holdover
persist 600 timer starts. During this period, the time properties flags
(currentUtcOffset, currentUtcOffsetValid, leap61, leap59)
persist for the holdover timeout period. Once the holdover
timer expires, currentUtcOffsetValid, leap59, and leap61
flags are set to false and the currentUtcOffset remains
unchanged. In case leap second midnight occurs when
holdover timer is running, utc-offset value is updated based
on leap59 or leap61 flags. This value is used as long as
there are no PTP packets being received from the selected
master. In case the selected master is sending announce
packets, the time-properties advertised by master is used.

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22
 Clocking and Timing
Configuring a Boundary Clock

Command or Action Purpose

Step 5 clock-port port-name {master | slave} [profile {g8265.1}] Sets the clock port to PTP master or slave mode; in slave
mode, the port exchanges timing packets with a PTP master
Example:
clock.
Router(config-ptp-clk)# clock-port SLAVE slave The profile keyword configures the clock to use the
G.8265.1 recommendations for establishing PTP sessions,
determining the best master clock, handling SSM, and
mapping PTP classes.
Note Using a telecom profile requires that the clock
have a domain number of 4–23.

Step 6 transport ipv4 unicast interface interface-type Specifies the transport mechanism for clocking traffic.
interface-number [negotiation]
The negotiation keyword configures the router to discover
Example: a PTP master clock from all available PTP clock sources.
Note PTP redundancy is supported only on unicast
Router(config-ptp-port)# transport ipv4 unicast
interface Loopback 0 negotiation negotiation mode.

Step 7 clock-source source-address [priority] Specifies the address of a PTP master clock. You can
specify a priority value as follows:
Example:
• No priority value—Assigns a priority value of 0.
Router(config-ptp-port)# clock source • 1—Assigns a priority value of 1.
133.133.133.133
• 2—Assigns a priority value of 2, the highest priority.

Step 8 clock-port port-name {master | slave} [profile {g8265.1}] Sets the clock port to PTP master or slave mode; in master
mode, the port exchanges timing packets with PTP slave
Example:
devices.
Router(config-ptp-port)# clock-port Master master Note The master clock-port does not establish a
clocking session until the slave clock-port is
phase aligned.
The profile keyword configures the clock to use the
G.8265.1 recommendations for establishing PTP sessions,
determining the best master clock, handling SSM, and
mapping PTP classes.
Note Using a telecom profile requires that the clock
have a domain number of 4–23.

Step 9 transport ipv4 unicast interface interface-type Specifies the transport mechanism for clocking traffic.
interface-number [negotiation]
The negotiation keyword configures the router to discover
Example: a PTP master clock from all available PTP clock sources.
Note PTP redundancy is supported only on unicast
Router(config-ptp-port)# transport ipv4 unicast
interface Loopback 1 negotiation negotiation mode.

Step 10 end Exit configuration mode.

Example:

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23
 Clocking and Timing
Configuring a Transparent Clock

Command or Action Purpose

Router(config-ptp-port)# end

Configuring a Transparent Clock

Follow these steps to configure the Cisco ASR 920 Series Router as an end-to-end transparent clock.

Note The Cisco ASR 920 Series Router does not support peer-to-peer transparent clock mode.

Note The transparent clock ignores the domain number.

SUMMARY STEPS
1. enable
2. configure terminal
3. ptp clock e2e-transparent domain domain-number
4. exit

DETAILED STEPS

Command or Action Purpose

Step 1 enable Enables privileged EXEC mode.
Example: • Enter your password if prompted.

Router> enable

Step 2 configure terminal Enter configuration mode.

Example:

Router# configure terminal

Step 3 ptp clock e2e-transparent domain domain-number Configures the router as an end-to-end transparent clock.
Example: • e2e-transparent—Updates the PTP time correction
field to account for the delay in forwarding the traffic.
Router(config)# ptp clock e2e-transparent domain This helps improve the accuracy of 1588 clock at slave.
0

Step 4 exit Exit configuration mode.

Example:

Router(config)# exit

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24
 Clocking and Timing
Configuring a Hybrid Boundary Clock

Configuring a Hybrid Boundary Clock

Follow these steps to configure a hybrid clocking in boundary clock mode.

Note When configuring a hybrid clock, ensure that the frequency and phase sources are traceable to the same master
clock.

SUMMARY STEPS
1. enable
2. configure terminal
3. ptp clock {ordinary | boundary} domain domain-number hybrid
4. time-properties persist value
5. utc-offset value leap-second “date time” offset {-1 | 1}
6. min-clock-class value
7. clock-port port-name {master | slave} [profile {g8265.1}]
8. transport ipv4 unicast interface interface-type interface-number [negotiation] [single-hop]
9. clock-source source-address [priority]
10. clock-port port-name {master | slave} [profile {g8265.1}]
11. transport ipv4 unicast interface interface-type interface-number [negotiation] [single-hop]
12. exit
13. network-clock synchronization automatic
14. network-clock synchronization mode ql-enabled
15. Use one of the following options:
• network-clock input-source <priority> controller {SONET | wanphy}
• network-clock input-source <priority> external {R0 | R1} [10m | 2m]
• network-clock input-source <priority> external {R0 | R1} [2048k | e1 {cas {120ohms | 75ohms |
crc4}}]
• network-clock input-source <priority> external {R0 | R1} [2048k | e1 {crc4 | fas] {120ohms |
75ohms} {linecode {ami | hdb3}}
• network-clock input-source <priority> external {R0 | R1} [t1 {d4 | esf | sf} {linecode {ami | b8zs}}]
• network-clock input-source <priority> interface <type/slot/port>
16. network-clock synchronization input-threshold ql value
17. network-clock hold-off {0 | milliseconds}
18. end

DETAILED STEPS

Command or Action Purpose

Step 1 enable Enables privileged EXEC mode.
Example: • Enter your password if prompted.

Router> enable

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25
 Clocking and Timing
Configuring a Hybrid Boundary Clock

Command or Action Purpose

Step 2 configure terminal Enter configuration mode.
Example:

Router# configure terminal

Step 3 ptp clock {ordinary | boundary} domain domain-number Configures the PTP clock. You can create the following
hybrid clock types:
Example: • ordinary—A 1588 clock with a single PTP port that
can operate in Master or Slave mode.
Router(config)# ptp clock ordinary domain 0 hybrid • boundary—Terminates PTP session from
Grandmaster and acts as PTP master to slaves
downstream.

Step 4 time-properties persist value (Optional) Starting with Cisco IOS-XE Release 3.18.1SP,
you can configure time properties holdover time. Valid
Example:
values are from 0 to 10000 seconds. The default value is
300 seconds.
Router(config-ptp-clk)# time-properties
persist 600 When a master clock is lost, the time properties holdover
timer starts. During this period, the time properties flags
(currentUtcOffset, currentUtcOffsetValid, leap61, leap59)
persist for the holdover timeout period. Once the holdover
timer expires, currentUtcOffsetValid, leap59, and leap61
flags are set to false and the currentUtcOffset remains
unchanged. In case leap second midnight occurs when
holdover timer is running, utc-offset value is updated based
on leap59 or leap61 flags. This value is used as long as
there are no PTP packets being received from the selected
master. In case the selected master is sending announce
packets, the time-properties advertised by master is used.

Step 5 utc-offset value leap-second “date time” offset {-1 | 1} (Optional) Starting with Cisco IOS-XE Release 3.18SP,
the new utc-offset CLI is used to set the UTC offset value.
Example:
Valid values are from 0-255. The default value is 36.
Router(config-ptp-clk)# utc-offset 45
(Optional) Starting with Cisco IOS-XE Release 3.18.1SP,
leap-second “01-01-2017 00:00:00” offset you can configure the current UTC offset, leap second
1 event date and Offset value (+1 or -1). Leap second
configuration will work only when the frequency source
is locked and ToD was up before.
• “date time”— Leap second effective date in
dd-mm-yyyy hh:mm:ss format.

Step 6 min-clock-class value Sets the threshold clock-class value. This allows the PTP
algorithm to use the time stamps from an upstream master
Example:
clock, only if the clock-class sent by the master clock is
less than or equal to the configured threshold clock-class.
Router(config-ptp-clk)# min-clock-class 157
Valid values are from 0-255.

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26
 Clocking and Timing
Configuring a Hybrid Boundary Clock

Command or Action Purpose

Note Min-clock-class value is supported only for PTP
with single master source configuration.

Step 7 clock-port port-name {master | slave} [profile {g8265.1}] Sets the clock port to PTP master or slave mode; in slave
mode, the port exchanges timing packets with a PTP master
Example:
clock.
Router(config-ptp-clk)# clock-port SLAVE slave Note Hybrid mode is only supported with slave
clock-ports; master mode is not supported.
The profile keyword configures the clock to use the
G.8265.1 recommendations for establishing PTP sessions,
determining the best master clock, handling SSM, and
mapping PTP classes.
Note Using a telecom profile requires that the clock
have a domain number of 4–23.

Step 8 transport ipv4 unicast interface interface-type Specifies the transport mechanism for clocking traffic.
interface-number [negotiation] [single-hop]
• negotiation—(Optional) configures the router to
Example: discover a PTP master clock from all available PTP
clock sources.
Router(config-ptp-port)# transport ipv4 unicast
interface Loopback 0 negotiation Note PTP redundancy is supported only on unicast
negotiation mode.
Example:
Note single-hop—(Optional) Must be configured,
Router(config-ptp-port)# transport ipv4 unicast if Hop-by-Hop PTP ring topology is used. It
interface Loopback 0 negotiation single-hop ensures that the PTP node communicates
only with the adjacent nodes.

Step 9 clock-source source-address [priority] Specifies the address of a PTP master clock. You can
specify a priority value as follows:
Example:
• No priority value—Assigns a priority value of 0.
Router(config-ptp-port)# clock source • 1—Assigns a priority value of 1.
133.133.133.133
• 2—Assigns a priority value of 2, the highest priority.

Step 10 clock-port port-name {master | slave} [profile {g8265.1}] Sets the clock port to PTP master or slave mode; in master
mode, the port exchanges timing packets with PTP slave
Example:
devices.
Router(config-ptp-port)# clock-port MASTER master The profile keyword configures the clock to use the
G.8265.1 recommendations for establishing PTP sessions,
determining the best master clock, handling SSM, and
mapping PTP classes.
Note Using a telecom profile requires that the clock
have a domain number of 4–23.

Step 11 transport ipv4 unicast interface interface-type Specifies the transport mechanism for clocking traffic.
interface-number [negotiation] [single-hop]

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27
 Clocking and Timing
Configuring a Hybrid Boundary Clock

Command or Action Purpose

Example: • negotiation—(Optional) configures the router to
discover a PTP master clock from all available PTP
Router(config-ptp-port)# transport ipv4 unicast clock sources.
interface Lo1 negotiation
Note PTP redundancy is supported only on unicast
Example: negotiation mode.

Router(config-ptp-port)# transport ipv4 unicast • single-hop—(Optional) Must be configured, if

interface Lo1 negotiation single-hop Hop-by-Hop PTP ring topology is used. It ensures
that the PTP node communicates only with the
adjacent nodes.

Step 12 exit Exits clock-port configuration.

Step 13 network-clock synchronization automatic Enables automatic selection of a clock source.

Example: Note This command is mandatory to configure the
leap second command.
Router(config)# network-clock synchronization
automatic Note This command must be configured before any
input source.

Step 14 network-clock synchronization mode ql-enabled Enables automatic selection of a clock source based on
quality level (QL).
Example:
Note This command is disabled by default.
Router(config)# network-clock synchronization mode
ql-enabled

Step 15 Use one of the following options: • (Optional) To nominate SDH or SONET controller
as network clock input source.
• network-clock input-source <priority> controller
{SONET | wanphy} • (Optional) To nominate 10Mhz port as network clock
input source.
• network-clock input-source <priority> external {R0
| R1} [10m | 2m] • (Optional) To nominate BITS port as network clock
input source in e1 mode.
• network-clock input-source <priority> external {R0
| R1} [2048k | e1 {cas {120ohms | 75ohms | crc4}}] • (Optional) To nominate BITS port as network clock
input source in e1 mode.
• network-clock input-source <priority> external {R0
| R1} [2048k | e1 {crc4 | fas] {120ohms | 75ohms} • (Optional) To nominate BITS port as network clock
{linecode {ami | hdb3}} input source in t1 mode.
• network-clock input-source <priority> external {R0 • (Optional) To nominate Ethernet interface as network
| R1} [t1 {d4 | esf | sf} {linecode {ami | b8zs}}] clock input source.
• network-clock input-source <priority> interface
<type/slot/port>
Example:

Router(config)# network-clock input-source 1

external R0 10m

Step 16 network-clock synchronization input-threshold ql value (Optional) Starting with Cisco IOS-XE Release 3.18SP,
this new CLI is used to set the threshold QL value for the
Example:
input frequency source. The input frequency source, which

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28
 Clocking and Timing
Configuring a Hybrid Ordinary Clock

Command or Action Purpose

is better than or equal to the configured threshold QL value,
network-clock
Router(config)# will be selected to recover the frequency. Otherwise,
synchronization input-threshold ql value internal clock is selected.

Step 17 network-clock hold-off {0 | milliseconds} (Optional) Configures a global hold-off timer specifying
the amount of time that the router waits when a
Example:
synchronous Ethernet clock source fails before taking
action.
Router(config)# network-clock hold-off 0
Note You can also specify a hold-off value for an
individual interface using the network-clock
hold-off command in interface mode.

Step 18 end Exit configuration mode.

Example:

Router(config)# end

Configuring a Hybrid Ordinary Clock

Follow these steps to configure a hybrid clocking in ordinary clock slave mode.

Note When configuring a hybrid clock, ensure that the frequency and phase sources are traceable to the same master
clock.

SUMMARY STEPS
1. enable
2. configure terminal
3. ptp clock {ordinary | boundary} domain domain-number hybrid
4. output [1pps] {R0 | R1} [offset offset-value] [pulse-width value]
5. tod {R0 | R1} {ubx | nmea | cisco | ntp}
6. clock-port port-name {master | slave} [profile {g8265.1}]
7. transport ipv4 unicast interface interface-type interface-number [negotiation]
8. clock-source source-address [priority]
9. exit
10. Use one of the following options:
• network-clock input-source <priority> controller {SONET | wanphy}
• network-clock input-source <priority> external {R0 | R1} [10m | 2m]
• network-clock input-source <priority> external {R0 | R1} [2048k | e1 {cas {120ohms | 75ohms |
crc4}}]
• network-clock input-source <priority> external {R0 | R1} [2048k | e1 {crc4 | fas] {120ohms |
75ohms} {linecode {ami | hdb3}}
• network-clock input-source <priority> external {R0 | R1} [t1 {d4 | esf | sf} {linecode {ami | b8zs}}]

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29
 Clocking and Timing
Configuring a Hybrid Ordinary Clock

• network-clock input-source <priority> interface <type/slot/port>

11. network-clock synchronization mode ql-enabled
12. network-clock hold-off {0 | milliseconds}
13. end

DETAILED STEPS

Command or Action Purpose

Step 1 enable Enables privileged EXEC mode.
Example: • Enter your password if prompted.

Router> enable

Step 2 configure terminal Enter configuration mode.

Example:

Router# configure terminal

Step 3 ptp clock {ordinary | boundary} domain domain-number Configures the PTP clock. You can create the following
hybrid clock types:
Example: • ordinary—A 1588 clock with a single PTP port that
can operate in Master or Slave mode.
Router(config)# ptp clock ordinary domain 0 hybrid • boundary—Terminates PTP session from
Grandmaster and acts as PTP master to slaves
downstream.

Step 4 output [1pps] {R0 | R1} [offset offset-value] [pulse-width Enables Precision Time Protocol input 1PPS using a 1PPS
value] input port.
Example: Use R0 or R1 to specify the active RSP slot.
Note Effective Cisco IOS XE Everest 16.6.1, on the
Router(config-ptp-clk)# output 1pps R0 offset 200
pulse-width 20 μsec Cisco ASR-920-12SZ-IM router, the 1pps pulse
bandwith can be changed from the default value
of 500 milliseconds to up to 20 microsecond.

Step 5 tod {R0 | R1} {ubx | nmea | cisco | ntp} Configures the time of day message format used by the
ToD interface.
Example:
Note The ToD port acts as an input port in case of
Router(config-ptp-clk)# tod R0 ntp Master clock and as an output port in case of
Slave clock.

Step 6 clock-port port-name {master | slave} [profile {g8265.1}] Sets the clock port to PTP master or slave mode; in slave
mode, the port exchanges timing packets with a PTP master
Example:
clock.
Router(config-ptp-clk)# clock-port SLAVE slave Note Hybrid mode is only supported with slave
clock-ports; master mode is not supported.

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 Clocking and Timing
Configuring a Hybrid Ordinary Clock

Command or Action Purpose

The profile keyword configures the clock to use the
G.8265.1 recommendations for establishing PTP sessions,
determining the best master clock, handling SSM, and
mapping PTP classes.
Note Using a telecom profile requires that the clock
have a domain number of 4–23.

Step 7 transport ipv4 unicast interface interface-type Specifies the transport mechanism for clocking traffic.
interface-number [negotiation]
The negotiation keyword configures the router to discover
Example: a PTP master clock from all available PTP clock sources.
Note PTP redundancy is supported only on unicast
Router(config-ptp-port)# transport ipv4 unicast
interface Loopback 0 negotiation negotiation mode.

Step 8 clock-source source-address [priority] Specifies the address of a PTP master clock. You can
specify a priority value as follows:
Example:
• No priority value—Assigns a priority value of 0.
Router(config-ptp-port)# clock source • 1—Assigns a priority value of 1.
133.133.133.133
• 2—Assigns a priority value of 2, the highest priority.

Step 9 exit Exit clock-port configuration.

Example:

Router(config-ptp-port)# exit

Step 10 Use one of the following options: • (Optional) To nominate SDH or SONET controller
as network clock input source.
• network-clock input-source <priority> controller
{SONET | wanphy} • (Optional) To nominate 10Mhz port as network clock
input source.
• network-clock input-source <priority> external {R0
| R1} [10m | 2m] • (Optional) To nominate BITS port as network clock
input source in e1 mode.
• network-clock input-source <priority> external {R0
| R1} [2048k | e1 {cas {120ohms | 75ohms | crc4}}] • (Optional) To nominate BITS port as network clock
input source in e1 mode.
• network-clock input-source <priority> external {R0
| R1} [2048k | e1 {crc4 | fas] {120ohms | 75ohms} • (Optional) To nominate BITS port as network clock
{linecode {ami | hdb3}} input source in t1 mode.
• network-clock input-source <priority> external {R0 • (Optional) To nominate Ethernet interface as network
| R1} [t1 {d4 | esf | sf} {linecode {ami | b8zs}}] clock input source.
• network-clock input-source <priority> interface
<type/slot/port>
Example:

Router(config)# network-clock input-source 1

external R0 10m

Step 11 network-clock synchronization mode ql-enabled Enables automatic selection of a clock source based on
quality level (QL).
Example:
Note This command is disabled by default.

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 Clocking and Timing
Configuring PTP Redundancy

Command or Action Purpose

Router(config-ptp-clk)# network-clock
synchronization mode ql-enabled

Step 12 network-clock hold-off {0 | milliseconds} (Optional) Configures a global hold-off timer specifying
the amount of time that the router waits when a
Example:
synchronous Ethernet clock source fails before taking
action.
Router(config-ptp-clk)# network-clock hold-off 0
Note You can also specify a hold-off value for an
individual interface using the network-clock
hold-off command in interface mode.

Step 13 end Exit configuration mode.

Example:

Router(config-ptp-clk)# end

Configuring PTP Redundancy

The following sections describe how to configure PTP redundancy on the Cisco ASR 920 Series Router:

Configuring PTP Redundancy in Slave Clock Mode

Follow these steps to configure clocking redundancy in slave clock mode:

SUMMARY STEPS
1. enable
2. configure terminal
3. ptp clock {ordinary | boundary} domain domain-number [hybrid]
4. ptp clock e2e-transparent domain domain-number
5. clock-port port-name {master | slave} [profile {g8265.1}]
6. transport ipv4 unicast interface interface-type interface-number [negotiation] [single-hop]
7. clock-source source-address [priority]
8. clock-source source-address [priority]
9. clock-source source-address [priority]
10. end

DETAILED STEPS

Command or Action Purpose

Step 1 enable Enables privileged EXEC mode.
Example: • Enter your password if prompted.

Router> enable

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32
 Clocking and Timing
Configuring PTP Redundancy in Slave Clock Mode

Command or Action Purpose

Step 2 configure terminal Enter configuration mode.
Example:

Router# configure terminal

Step 3 ptp clock {ordinary | boundary} domain domain-number Configures the PTP clock. You can create the following
[hybrid] clock types:
Example: • ordinary—A 1588 clock with a single PTP port that
can operate in Master or Slave mode.
Router(config)# ptp clock ordinary domain 0 • boundary—Terminates PTP session from
Grandmaster and acts as PTP master to slaves
downstream.

Step 4 ptp clock e2e-transparent domain domain-number Configures the PTP clock.
Example: • e2e-transparent—Updates the PTP time correction
field to account for the delay in forwarding the traffic.
Router(config)# ptp clock e2e-transparent domain This helps improve the accuracy of 1588 clock at
0 slave.

Step 5 clock-port port-name {master | slave} [profile {g8265.1}] Sets the clock port to PTP master or slave mode; in slave
mode, the port exchanges timing packets with a PTP master
Example:
clock.
Router(config-ptp-clk)# clock-port SLAVE slave The profile keyword configures the clock to use the
G.8265.1 recommendations for establishing PTP sessions,
determining the best master clock, handling SSM, and
mapping PTP classes.
Note Using a telecom profile requires that the clock
have a domain number of 4–23.

Step 6 transport ipv4 unicast interface interface-type Specifies the transport mechanism for clocking traffic.
interface-number [negotiation] [single-hop]
• negotiation—(Optional) Configures the router to
Example: discover a PTP master clock from all available PTP
clock sources.
Router(config-ptp-port)# transport ipv4 unicast
interface Loopback 0 negotiation Note PTP redundancy is supported only on unicast
negotiation mode.
Example:
• single-hop—(Optional) It ensures that the PTP
Router(config-ptp-port)# transport ipv4 unicast node communicates only with the adjacent nodes.
interface Loopback 0 negotiation single-hop

Step 7 clock-source source-address [priority] Specifies the address of a PTP master clock. You can
specify a priority value as follows:
Example:
• No priority value—Assigns a priority value of 0.
Router(config-ptp-port)# clock source • 1—Assigns a priority value of 1.
133.133.133.133 1
• 2—Assigns a priority value of 2, the highest priority.

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33
 Clocking and Timing
Configuring PTP Redundancy in Boundary Clock Mode

Command or Action Purpose

Step 8 clock-source source-address [priority] Specifies the address of an additional PTP master clock;
repeat this step for each additional master clock. You can
Example:
configure up to 3 master clocks.
Router(config-ptp-port)# clock source
133.133.133.134 2

Step 9 clock-source source-address [priority] Specifies the address of an additional PTP master clock;
repeat this step for each additional master clock. You can
Example:
configure up to 3 master clocks.
Router(config-ptp-port)# clock source
133.133.133.135

Step 10 end Exit configuration mode.

Example:

Router(config-ptp-port)# end

Configuring PTP Redundancy in Boundary Clock Mode

Follow these steps to configure clocking redundancy in boundary clock mode:

SUMMARY STEPS
1. enable
2. Router# configure terminal
3. ptp clock {ordinary | boundary} domain domain-number [hybrid]
4. ptp clock e2e-transparent domain domain-number
5. clock-port port-name {master | slave} [profile {g8265.1}]
6. transport ipv4 unicast interface interface-type interface-number [negotiation] [single-hop]
7. clock-source source-address [priority]
8. clock-source source-address [priority]
9. clock-source source-address [priority]
10. clock-port port-name {master | slave} [profile {g8265.1}]
11. transport ipv4 unicast interface interface-type interface-number [negotiation] [single-hop]
12. end

DETAILED STEPS

Command or Action Purpose

Step 1 enable Enables privileged EXEC mode.
Example: • Enter your password if prompted.

Router> enable

Step 2 Router# configure terminal Enter configuration mode.

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34
 Clocking and Timing
Configuring PTP Redundancy in Boundary Clock Mode

Command or Action Purpose

Step 3 ptp clock {ordinary | boundary} domain domain-number Configures the PTP clock. You can create the following
[hybrid] clock types:
Example: • ordinary—A 1588 clock with a single PTP port that
can operate in Master or Slave mode.
Router(config)# ptp clock ordinary domain 0 • boundary—Terminates PTP session from
Grandmaster and acts as PTP master to slaves
downstream.

Step 4 ptp clock e2e-transparent domain domain-number Configures the PTP clock.
Example: • e2e-transparent—Updates the PTP time correction
field to account for the delay in forwarding the traffic.
Router(config)# ptp clock e2e-transparent domain This helps improve the accuracy of 1588 clock at
0 slave.

Step 5 clock-port port-name {master | slave} [profile {g8265.1}] Sets the clock port to PTP master or slave mode; in slave
mode, the port exchanges timing packets with a PTP master
Example:
clock.
Router(config-ptp-clk)# clock-port SLAVE slave The profile keyword configures the clock to use the
G.8265.1 recommendations for establishing PTP sessions,
determining the best master clock, handling SSM, and
mapping PTP classes.
Note Using a telecom profile requires that the clock
have a domain number of 4–23.

Step 6 transport ipv4 unicast interface interface-type Specifies the transport mechanism for clocking traffic.
interface-number [negotiation] [single-hop]
• negotiation—(Optional) Configures the router to
Example: discover a PTP master clock from all available PTP
clock sources.
Router(config-ptp-port)# transport ipv4 unicast
interface Loopback 0 negotiation Note PTP redundancy is supported only on unicast
negotiation mode.
Example:
• single-hop—(Optional) Must be configured, if
Router(config-ptp-port)# transport ipv4 unicast Hop-by-Hop PTP ring topology is used. It ensures
interface Loopback 0 negotiation single-hop that the PTP node communicates only with the
adjacent nodes.

Step 7 clock-source source-address [priority] Specifies the address of a PTP master clock. You can
specify a priority value as follows:
Example:
• No priority value—Assigns a priority value of 0.
Router(config-ptp-port)# clock source • 1—Assigns a priority value of 1.
133.133.133.133 1
• 2—Assigns a priority value of 2, the highest priority.

Step 8 clock-source source-address [priority] Specifies the address of an additional PTP master clock;
repeat this step for each additional master clock. You can
Example:
configure up to 3 master clocks.
Router(config-ptp-port)# clock source
133.133.133.134 2

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35
 Clocking and Timing
Synchronizing the System Time to a Time-of-Day Source

Command or Action Purpose

Step 9 clock-source source-address [priority] Specifies the address of an additional PTP master clock;
repeat this step for each additional master clock. You can
Example:
configure up to 3 master clocks.
Router(config-ptp-port)# clock source
133.133.133.135

Step 10 clock-port port-name {master | slave} [profile {g8265.1}] Specifies the address of a PTP master clock.
Example: The profile keyword configures the clock to use the
G.8265.1 recommendations for establishing PTP sessions,
Router(config-ptp-port)# clock-port MASTER master determining the best master clock, handling SSM, and
mapping PTP classes.
Note Using a telecom profile requires that the clock
have a domain number of 4–23.

Step 11 transport ipv4 unicast interface interface-type Specifies the transport mechanism for clocking traffic.
interface-number [negotiation] [single-hop]
• negotiation—(Optional) Configures the router to
Example: discover a PTP master clock from all available PTP
clock sources.
Router(config-ptp-port)# transport ipv4 unicast
interface Loopback 1 negotiation single-hop Note PTP redundancy is supported only on unicast
negotiation mode.
• single-hop—(Optional) Must be configured if
Hop-by-Hop PTP ring topology is used. It ensures
that the PTP node communicates only with the
adjacent nodes

Step 12 end Exit configuration mode.

Example:

Router(config-ptp-port)# end

Synchronizing the System Time to a Time-of-Day Source

The following sections describe how to synchronize the system time to a time of day (ToD) clock source.

Synchronizing the System Time to a Time-of-Day Source (Master Mode)

Note System time to a ToD source (Master Mode) can be configured only when PTP master is configured. See
Configuring a Master Ordinary Clock, on page 14. Select any one of the four available ToD format; cisco,
nmea, ntp or ubx.10m must be configured as network clock input source.

Follow these steps to configure the system clock to a ToD source in master mode.

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36
 Clocking and Timing
Synchronizing the System Time to a Time-of-Day Source (Slave Mode)

SUMMARY STEPS
1. enable
2. configure terminal
3. tod-clock input-source priority {gps {R0 | R1} | ptp domain domain}
4. exit

DETAILED STEPS

Command or Action Purpose

Step 1 enable Enables privileged EXEC mode.
Example: • Enter your password if prompted.

Router> enable

Step 2 configure terminal Enter configuration mode.

Example:

Router# configure terminal

Step 3 tod-clock input-source priority {gps {R0 | R1} | ptp In master mode, specify a GPS port connected to a ToD
domain domain} source.
Example:

Router(config)# TOD-clock 2 gps R0/R1

Step 4 exit Exit configuration mode.

Example:

Router(config)# exit

Synchronizing the System Time to a Time-of-Day Source (Slave Mode)

Note System time to a ToD source (Slave Mode) can be configured only when PTP slave is configured. See
Configuring a Slave Ordinary Clock, on page 19.

Follow these steps to configure the system clock to a ToD source in slave mode. In slave mode, specify a PTP
domain as a ToD input source.

SUMMARY STEPS
1. enable
2. configure terminal
3. tod-clock input-source priority {gps {R0 | R1} | ptp domain domain}
4. Router(config)# end

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37
 Clocking and Timing
Synchronous Ethernet ESMC and SSM

DETAILED STEPS

Command or Action Purpose

Step 1 enable Enables privileged EXEC mode.
Example: • Enter your password if prompted.

Router> enable

Step 2 configure terminal Enter configuration mode.

Example:

Router# configure terminal

Step 3 tod-clock input-source priority {gps {R0 | R1} | ptp In slave mode, specify a PTP domain as a ToD input source.
domain domain}
Example:

Router(config)# TOD-clock 10 ptp domain 0

Step 4 Router(config)# end Exit configuration mode.

Synchronous Ethernet ESMC and SSM

Synchronous Ethernet is an extension of Ethernet designed to provide the reliability found in traditional
SONET/SDH and T1/E1 networks to Ethernet packet networks by incorporating clock synchronization features.
The supports the Synchronization Status Message (SSM) and Ethernet Synchronization Message Channel
(ESMC) for synchronous Ethernet clock synchronization.

Configuring Synchronous Ethernet ESMC and SSM

Follow these steps to configure ESMC and SSM on the Cisco ASR 920 Series Router:

SUMMARY STEPS
1. enable
2. configure terminal
3. network-clock synchronization automatic
4. network-clock eec {1 | 2}
5. network-clock synchronization ssm option {1 | 2 {GEN1 | GEN2}}
6. Use one of the following options:
• network-clock input-source <priority> controller {SONET | wanphy}
• network-clock input-source <priority> external {R0 | R1} [10m | 2m]
• network-clock input-source <priority> external {R0 | R1} [2048k | e1 {cas {120ohms | 75ohms |
crc4}}]
• network-clock input-source <priority> external {R0 | R1} [2048k | e1 {crc4 | fas] {120ohms |
75ohms} {linecode {ami | hdb3}}
• network-clock input-source <priority> external {R0 | R1} [t1 {d4 | esf | sf} {linecode {ami | b8zs}}]
• network-clock input-source <priority> interface <type/slot/port>

Clocking and Timing

38
 Clocking and Timing
Configuring Synchronous Ethernet ESMC and SSM

• network-clock input-source <priority> ptp domain <domain-number>

7. network-clock synchronization mode ql-enabled
8. network-clock hold-off {0 | milliseconds}
9. network-clock wait-to-restore seconds
10. network-clock revertive
11. esmc process
12. network-clock external slot/card/port hold-off {0 | milliseconds}
13. network-clock quality-level {tx | rx} value {controller [E1| BITS] slot/card/port | external [2m | 10m
| 2048k | t1 | e1] }
14. interface type number
15. synchronous mode
16. network-clock source quality-level value {tx | rx}
17. esmc mode [ql-disabled | tx | rx] value
18. network-clock hold-off {0 | milliseconds}
19. network-clock wait-to-restore seconds
20. end

DETAILED STEPS

Command or Action Purpose

Step 1 enable Enables privileged EXEC mode.
Example: • Enter your password if prompted.

Router> enable

Step 2 configure terminal Enters global configuration mode.

Example:

Router# configure terminal

Step 3 network-clock synchronization automatic Enables the network clock selection algorithm. This
command disables the Cisco-specific network clock
Example:
process and turns on the G.781-based automatic clock
selection process.
Router(config)# network-clock synchronization
automatic Note This command must be configured before any
input source.

Step 4 network-clock eec {1 | 2} Specifies the Ethernet Equipment Clock (EEC) type. Valid
values are
Example:
• 1—ITU-T G.8262 option 1 (2048)
Router(config)# network-clock eec 1 • 2—ITU-T G.8262 option 2 and Telcordia GR-1244
(1544)

Step 5 network-clock synchronization ssm option {1 | 2 {GEN1 Configures the G.781 synchronization option used to send
| GEN2}} synchronization messages. The following guidelines apply
for this command:
Example:

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39
 Clocking and Timing
Configuring Synchronous Ethernet ESMC and SSM

Command or Action Purpose

• Option 1 refers to G.781 synchronization option 1,
Router(config)# network-clock synchronization ssm
which is designed for Europe. This is the default
option 2 GEN2
value.
• Option 2 refers to G.781 synchronization option 2,
which is designed for the United States.
• GEN1 specifies option 2 Generation 1
synchronization.
• GEN2 specifies option 2 Generation 2
synchronization.

Step 6 Use one of the following options: • (Optional) To nominate SDH or SONET controller
as network clock input source.
• network-clock input-source <priority> controller
{SONET | wanphy} • (Optional) To nominate 10Mhz port as network clock
input source.
• network-clock input-source <priority> external {R0
| R1} [10m | 2m] • (Optional) To nominate BITS port as network clock
input source in e1 mode.
• network-clock input-source <priority> external {R0
| R1} [2048k | e1 {cas {120ohms | 75ohms | crc4}}] • (Optional) To nominate BITS port as network clock
input source in e1 mode.
• network-clock input-source <priority> external {R0
| R1} [2048k | e1 {crc4 | fas] {120ohms | 75ohms} • (Optional) To nominate BITS port as network clock
{linecode {ami | hdb3}} input source in t1 mode.
• network-clock input-source <priority> external {R0 • (Optional) To nominate Ethernet interface as network
| R1} [t1 {d4 | esf | sf} {linecode {ami | b8zs}}] clock input source.
• network-clock input-source <priority> interface • (Optional) To nominate PTP as network clock input
<type/slot/port> source.
• network-clock input-source <priority> ptp domain
<domain-number>
Example:

Router(config)# network-clock input-source 1

external R0 10m

Step 7 network-clock synchronization mode ql-enabled Enables automatic selection of a clock source based on
quality level (QL).
Example:
Note This command is disabled by default.
Router(config)# network-clock synchronization mode
ql-enabled

Step 8 network-clock hold-off {0 | milliseconds} (Optional) Configures a global hold-off timer specifying
the amount of time that the router waits when a
Example:
synchronous Ethernet clock source fails before taking
action.
Router(config)# network-clock hold-off 0
Note You can also specify a hold-off value for an
individual interface using the network-clock
hold-off command in interface mode.

Step 9 network-clock wait-to-restore seconds (Optional) Configures a global wait-to-restore timer for
synchronous Ethernet clock sources. The timer specifies
Example:

Clocking and Timing

40
 Clocking and Timing
Configuring Synchronous Ethernet ESMC and SSM

Command or Action Purpose

how long the router waits before including a restored clock
Router(config)# network-clock wait-to-restore 70
source in the clock selection process.
Valid values are 0 to 86400 seconds. The default value is
300 seconds.
Note You can also specify a wait-to-restore value for
an individual interface using the network-clock
wait-to-restore command in interface mode.

Step 10 network-clock revertive (Optional) Sets the router in revertive switching mode
when recovering from a failure. To disable revertive mode,
Example:
use the no form of this command.
Router(config)# network-clock revertive

Step 11 esmc process Enables the ESMC process globally.

Example:

Router(config)# esmc process

Step 12 network-clock external slot/card/port hold-off {0 | Overrides the hold-off timer value for the external
milliseconds} interface.
Example:

Router(config)# network-clock external 0/1/0

hold-off 0

Step 13 network-clock quality-level {tx | rx} value {controller Specifies a quality level for a line or external clock source.
[E1| BITS] slot/card/port | external [2m | 10m | 2048k |
The available quality values depend on the G.781
t1 | e1] }
synchronization settings specified by the network-clock
Example: synchronization ssm option command:
• Option 1—Available values are QL-PRC, QL-SSU-A,
Router(config)# network-clock quality-level rx
qL-pRC external R0 e1 cas crc4 QL-SSU-B, QL-SEC, and QL-DNU.
• Option 2, GEN1—Available values are QL-PRS,
QL-STU, QL-ST2, QL-SMC, QL-ST4, and QL-DUS.
• Option 2, GEN 2—Available values are QL-PRS,
QL-STU, QL-ST2, QL-TNC, QL-ST3, QL-SMC,
QL-ST4, and QL-DUS.

Step 14 interface type number Enters interface configuration mode.

Example:

Router(config)# interface GigabitEthernet 0/0/1

Example:

Router(config-if)#

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41
 Clocking and Timing
Configuring Synchronous Ethernet ESMC and SSM

Command or Action Purpose

Step 15 synchronous mode Configures the Ethernet interface to synchronous mode
and automatically enables the ESMC and QL process on
Example:
the interface.
Router(config-if)# synchronous mode

Step 16 network-clock source quality-level value {tx | rx} Applies quality level on sync E interface.
Example: The available quality values depend on the G.781
synchronization settings specified by the network-clock
Router(config-if)# network-clock source synchronization ssm option command:
quality-level QL-PrC tx
• Option 1—Available values are QL-PRC, QL-SSU-A,
QL-SSU-B, QL-SEC, and QL-DNU.
• Option 2, GEN1—Available values are QL-PRS,
QL-STU, QL-ST2, QL-SMC, QL-ST4, and QL-DUS.
• Option 2, GEN 2—Available values are QL-PRS,
QL-STU, QL-ST2, QL-TNC, QL-ST3, QL-SMC,
QL-ST4, and QL-DUS.

Step 17 esmc mode [ql-disabled | tx | rx] value Enables the ESMC process at the interface level. The no
form of the command disables the ESMC process.
Example:

Router(config-if)# esmc mode rx QL-STU

Step 18 network-clock hold-off {0 | milliseconds} (Optional) Configures an interface-specific hold-off timer

specifying the amount of time that the router waits when
Example:
a synchronous Ethernet clock source fails before taking
action.
Router(config-if)# network-clock hold-off 0
You can configure the hold-off time to either 0 or any
value between 50 to 10000 ms. The default value is 300
ms.

Step 19 network-clock wait-to-restore seconds (Optional) Configures the wait-to-restore timer for an
individual synchronous Ethernet interface.
Example:

Router(config-if)# network-clock wait-to-restore

70

Step 20 end Exits interface configuration mode and returns to privileged

EXEC mode.
Example:

Router(config-if)# end

What to do next
You can use the show network-clocks command to verify your configuration.

Clocking and Timing

42
 Clocking and Timing
Specifying a Clock Source

Specifying a Clock Source

The following sections describe how to specify a synchronous Ethernet clock source during the clock selection
process:

Selecting a Specific Clock Source

To select a specific interface as a synchronous Ethernet clock source, use the network-clock switch manual
command in global configuration mode.

Note The new clock source must be of higher quality than the current clock source; otherwise the router does not
select the new clock source.

Command Purpose

network-clock switch manual external R0 | Manually selects a synchronization source,

R1 {{E1 {crc4 | cas |fas}} {T1 {d4 | sf | esf}} provided the source is available and is within
} the range.

Router# network-clock switch manual external r0 e1

crc4

network-clock clear switch {t0 | external slot/card/port [10m Disable a clock source selection.
| 2m]}

Router# network-clock clear switch t0

Forcing a Clock Source Selection

To force the router to use a specific synchronous Ethernet clock source, use the network-clock switch force
command in global configuration mode.

Note This command selects the new clock regardless of availability or quality.

Note Forcing a clock source selection overrides a clock selection using the network-clock switch manual command.

Command Purpose

network-clock switch force external R0 | R1 {{E1 {crc4 Forces the router to use a specific synchronous
| cas |fas}} {T1 {d4 | sf | esf}} } Ethernet clock source, regardless of clock
quality or availability.
Router# network-clock switch force r0 e1 crc4

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43
 Clocking and Timing
Disabling a Clock Source

Command Purpose

network-clock clear switch {t0 | external slot/card/port Disable a clock source selection.
[10m | 2m]}

Router# network-clock clear switch t0

Disabling Clock Source Specification Commands

To disable a network-clock switch manual or network-clock switch force configuration and revert to the
default clock source selection process, use the network-clock clear switch command.

Command Purpose

network-clock clear switch {t0 | external slot/card/port [10m | 2m]} Disable a clock source selection.

Router# network-clock clear switch t0

Disabling a Clock Source

The following sections describe how to manage the synchronous Ethernet clock sources that are available for
clock selection:

Locking Out a Clock Source

To prevent the router from selecting a specific synchronous Ethernet clock source, use the network-clock set
lockout command in global configuration mode.

Command Purpose

network-clock set lockout {interface Prevents the router from selecting a

interface_name slot/card/port | external {R0 | R1 [ { specific synchronous Ethernet clock
t1 {sf | esf } linecode {ami | b8zs}} | e1 [crc4 source.
| fas] linecode [hdb3 | ami]}

Router# network-clock set lockout interface GigabitEthernet

0/0/0

network-clock clear lockout {interface interface_name Disable a lockout configuration on a

slot/card/port | external {R0 | R1 [ { t1 {sf | esf } linecode {ami | synchronous Ethernet clock source.
b8zs}} | e1 [crc4 | fas] linecode [hdb3 | ami] }

Router# network-clock clear lockout interface

GigabitEthernet 0/0/0

Restoring a Clock Source

To restore a clock in a lockout condition to the pool of available clock sources, use the network-clock clear
lockout command in global configuration mode.

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 Clocking and Timing
Verifying the Configuration

Command Purpose

network-clock clear lockout {interface Forces the router to use a specific

interface_name slot/card/port | external external synchronous Ethernet clock source,
{R0 | R1 [ { t1 {sf | esf } linecode {ami | regardless of clock quality or availability.
b8zs}} | e1 [crc4 | fas] linecode [hdb3 | ami]
}

Router# network-clock clear lockout interface

GigabitEthernet 0/0/0

Verifying the Configuration

You can use the following commands to verify a clocking configuration:
• show esmc—Displays the ESMC configuration.
• show esmc detail—Displays the details of the ESMC parameters at the global and interface levels.
• show network-clock synchronization—Displays the router clock synchronization state.
• show network-clock synchronization detail—Displays the details of network clock synchronization
parameters at the global and interface levels.
• show ptp clock dataset
• show ptp port dataset
• show ptp clock running
• show platform software ptpd statistics
• show platform ptp all
• show platform ptp tod all

Troubleshooting
The below table list the debug commands that are available for troubleshooting the SyncE configuration on
the Cisco ASR 920 Series Router:

Caution We recommend that you do not use debug commands without TAC supervision.

Table 7: SyncE Debug Commands

Debug Command Purpose

debug platform network-clock Debugs issues related to the network clock including
active-standby selection, alarms, and OOR messages.

debug network-clock Debugs issues related to network clock selection.

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Troubleshooting

Debug Command Purpose

debug esmc error These commands verify whether the ESMC packets are
transmitted and received with proper quality-level values.
debug esmc event
debug esmc packet [interface interface-name]
debug esmc packet rx [interface interface-name]
debug esmc packet tx [interface interface-name]

The below table provides the information about troubleshooting your configuration

Table 8: Troubleshooting Scenarios

Problem Solution

Clock selection • Verify that there are no alarms on the interfaces using the show
network-clock synchronization detail command.
• Ensure that the nonrevertive configurations are in place.
• Reproduce the issue and collect the logs using the debug network-clock
errors, debug network-clock event, and debug network-clock sm
commands. Contact Cisco Technical Support if the issue persists.

Incorrect QL values • Ensure that there is no framing mismatch with the SSM option.
• Reproduce the issue using the debug network-clock errors and debug
network-clock event commands.

Alarms • Reproduce the issue using the debug platform network-clock command
enabled in the RSP. Alternatively, enable the debug network-clock event
and debug network-clock errors commands.

Incorrect clock limit set or • Verify that there are no alarms on the interfaces using the show
queue limit disabled mode network-clock synchronization detail command.
• Use the show network-clock synchronization command to confirm if
the system is in revertive mode or nonrevertive mode and verify the
non-revertive configurations.
• Reproduce the current issue and collect the logs using the debug
network-clock errors, debug network-clock event, and debug network-clock
sm RSP commands.

Incorrect QL values when • Use the network clock synchronization SSM (option 1 |option 2)
you use the show command to confirm that there is no framing mismatch. Use the show
network-clock run interface command to validate the framing for a specific interface.
synchronization detail For the SSM option 1, framing should be SDH or E1, and for SSM option
command. 2, it should be T1.
• Reproduce the issue using the debug network-clock errors and debug
network-clock event RSP commands.

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Configuration Examples

Configuration Examples
This section contains sample configurations for clocking features on the Cisco ASR 920 Series Router.

Note This section contains partial router configurations intended to demonstrate a specific feature.

Ordinary Clock—Slave

ptp clock ordinary domain 0

clock-port Slave slave
transport ipv4 unicast interface loopback 0 negotiation
clock-source 8.8.8.1
announce timeout 7
delay-req interval 100

Ordinary Clock —Slave Mode (Ethernet)

ptp clock ordinary domain 0

clock-port Slave slave
transport ethernet unicast
clock-source 1234.5678.90ab bridge-domain 5 2

Ordinary Clock—Master

ptp clock ordinary domain 0

clock-port Master master
transport ipv4 unicast interface loopback 0 negotiation

Ordinary Clock—Master (Ethernet)

ptp clock ordinary domain 0

clock-port Master master
transport ethernet unicast
clock destination interface GigabitEthernet0/0/1

Unicast Configuration—Slave Mode

ptp clock ordinary domain 0

clock-port Slave slave
transport ipv4 unicast interface loopback 0
clock-source 8.8.8.1

Unicast Configuration—Slave Mode (Ethernet)

ptp clock ordinary domain 0

clock-port Slave slave
transport ethernet unicast
clock source 1234.5678.90ab bridge-domain 5 2

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Configuration Examples

Unicast Configuration—Master Mode

ptp clock ordinary domain 0

clock-port Master master
transport ipv4 unicast interface loopback 0
clock-destination 8.8.8.2
sync interval 1
announce interval 2

Unicast Configuration—Master Mode (Ethernet)

ptp clock ordinary domain 0

clock-port Master master
transport ethernet unicast
clock destination 1234.5678.90ab bridge-domain 5

Unicast Negotiation—Slave

ptp clock ordinary domain 0

clock-port Slave slave
transport ipv4 unicast interface loopback 0 negotiation
clock-source 8.8.8.1

Unicast Negotiation—Slave (Ethernet)

ptp clock ordinary domain 0

clock-port Slave slave
transport ethernet unicast negotiation
clock source 1234.5678.90ab bridge-domain 5 5
clock-port Slave1 slave
transport ethernet unicast negotiation
clock source 1234.9876.90ab interface gigabitethernet 0/0/4 2

Unicast Negotiation—Master

ptp clock ordinary domain 0

clock-port Master master
transport ipv4 unicast interface loopback 0 negotiation
sync interval 1
announce interval 2

Unicast Negotiation—Master (Ethernet)

ptp clock ordinary domain 0

clock-port Master master
transport ethernet unicast negotiation

Boundary Clock

ptp clock boundary domain 0

clock-port SLAVE slave
transport ipv4 unicast interface Loopback 0 negotiation
clock source 133.133.133.133
clock-port MASTER master
transport ipv4 unicast interface Loopback 1 negotiation

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Configuration Examples

Transparent Clock

ptp clock e2e-transparent domain 0

Hybrid Clock—Boundary

network-clock synchronization automatic

ptp clock boundary domain 0 hybrid
clock-port SLAVE slave
transport ipv4 unicast interface Loopback0 negotiation
clock source 133.133.133.133
clock-port MASTER master
transport ipv4 unicast interface Loopback1 negotiation
Network-clock input-source 10 interface gigabitEthernet 0/4/0

Hybrid Clock—Slave

network-clock synchronization automatic

ptp clock ordinary domain 0 hybrid
clock-port SLAVE slave
transport ipv4 unicast interface Loopback 0 negotiation
clock source 133.133.133.133

Network-clock input-source 10 interface gigabitEthernet 0/4/0

PTP Redundancy—Slave

ptp clock ordinary domain 0

clock-port SLAVE slave
transport ipv4 unicast interface Loopback 0 negotiation
clock source 133.133.133.133 1
clock source 55.55.55.55 2
clock source 5.5.5.5

PTP Redundancy—Boundary

ptp clock boundary domain 0

clock-port SLAVE slave
transport ipv4 unicast interface Loopback 0 negotiation
clock source 133.133.133.133 1
clock source 55.55.55.55 2
clock source 5.5.5.5
clock-port MASTER master
transport ipv4 unicast interface Lo1 negotiation

Hop-By-Hop PTP Redundancy—Slave

ptp clock ordinary domain 0

clock-port SLAVE slave
transport ipv4 unicast interface Loopback 0 negotiation single-hop
clock source 133.133.133.133 1
clock source 55.55.55.55 2
clock source 5.5.5.5

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Configuration Examples

Hop-By-Hop PTP Redundancy—Boundary

ptp clock boundary domain 0

clock-port SLAVE slave
transport ipv4 unicast interface Loopback 0 negotiation single-hop
clock source 133.133.133.133 1
clock source 55.55.55.55 2
clock source 5.5.5.5
clock-port MASTER master
transport ipv4 unicast interface Lo1 negotiation single-hop

Time of Day Source—Master

TOD-clock 10 gps R0/R1

Time of Day Source—Slave

TOD-clock 10 ptp R0/R1

Clock Selection Parameters

network-clock synchronization automatic

network-clock synchronization mode QL-enabled
network-clock input-source 1 ptp domain 3

ToD/1PPS Configuration—Master

network-clock input-source 1 external R010m

ptp clock ordinary domain 1
tod R0 ntp
input 1pps R0
clock-port master master
transport ipv4 unicast interface loopback 0

ToD/1PPS Configuration—Slave

ptp clock ordinary domain 1

tod R0 ntp
output 1pps R0 offset 200 pulse-width 20 μsec
clock-port SLA slave
transport ipv4 unicast interface loopback 0 negotiation
clock source 33.1.1.

Show Commands

Router# show ptp clock dataset ?

current currentDS dataset
default defaultDS dataset
parent parentDS dataset
time-properties timePropertiesDS dataset
Router# show ptp port dataset ?
foreign-master foreignMasterDS dataset
port portDS dataset
Router# show ptp clock running domain 0
PTP Ordinary Clock [Domain 0]

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Configuration Examples

State Ports Pkts sent Pkts rcvd Redundancy Mode

ACQUIRING 1 98405 296399 Track one
PORT SUMMARY
PTP Master
Name Tx Mode Role Transport State Sessions Port
Addr
SLAVE unicast slave Lo0 Slave 1
8.8.8.8
SESSION INFORMATION
SLAVE [Lo0] [Sessions 1]
Peer addr Pkts in Pkts out In Errs Out Errs
8.8.8.8 296399 98405 0 0
Router#
Router# show platform software ptpd stat stream 0
LOCK STATUS : PHASE LOCKED
SYNC Packet Stats
Time elapsed since last packet: 0.0
Configured Interval : 0, Acting Interval 0
Tx packets : 0, Rx Packets : 169681
Last Seq Number : 0, Error Packets : 1272
Delay Req Packet Stats
Time elapsed since last packet: 0.0
Configured Interval : 0, Acting Interval : 0
Tx packets : 84595, Rx Packets : 0
Last Seq Number : 19059, Error Packets : 0
!output omitted for brevity
Current Data Set
Offset from master : 0.4230440
Mean Path Delay : 0.0
Steps Removed 1
General Stats about this stream
Packet rate : 0, Packet Delta (ns) : 0
Clock Stream handle : 0, Index : 0
Oper State : 6, Sub oper State : 7
Log mean sync Interval : -5, log mean delay req int : -4
Router# show platform ptp all
Slave info : [Loopback0][0x38A4766C]
--------------------------------
clock role : SLAVE
Slave Port hdl : 486539266
Tx Mode : Unicast-Negotiation
Slave IP : 4.4.4.4
Max Clk Srcs : 1
Boundary Clock : FALSE
Lock status : HOLDOVER
Refcnt : 1
Configured-Flags : 0x7F - Clock Port Stream
Config-Ready-Flags : Port Stream
-----------
PTP Engine Handle : 0
Master IP : 8.8.8.8
Local Priority : 0
Set Master IP : 8.8.8.8
Router# show platform ptp tod all
--------------------------------
ToD/1PPS Info for 0/0
--------------------------------
ToD CONFIGURED : YES
ToD FORMAT : NMEA
ToD DELAY : 0
1PPS MODE : OUTPUT
OFFSET : 0
PULSE WIDTH : 0
ToD CLOCK : Mon Jan 1 00:00:00 UTC 1900

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Configuration Examples

Router# show ptp clock running domain 0

PTP Boundary Clock [Domain 0]
State Ports Pkts sent Pkts rcvd Redundancy Mode
PHASE_ALIGNED 2 32355 159516 Hot standby
PORT SUMMARY

PTP Master
Name Tx Mode Role Transport State Sessions Port Addr

SLAVE unicast slave Ethernet 1

9.9.9.1
MASTER unicast master Ethernet - 2 -
SESSION INFORMATION

SLAVE [Ethernet] [Sessions 1]

Peer addr Pkts in Pkts out In Errs Out Errs

9.9.9.1 159083 31054 0 0

MASTER [Ethernet] [Sessions 2]

Peer addr Pkts in Pkts out In Errs Out Errs
aabb.ccdd.ee01 [Gig0/2/3] 223 667 0 0
aabb.ccdd.ee02 [BD 1000] 210 634 0 0

Input Synchronous Ethernet Clocking

The following example shows how to configure the router to use the BITS interface and two Gigabit Ethernet
interfaces as input synchronous Ethernet timing sources. The configuration enables SSM on the BITS port.

!
Interface GigabitEthernet0/0
synchronous mode
network-clock wait-to-restore 720
!
Interface GigabitEthernet0/1
synchronous mode
!
!
network-clock synchronization automatic
network-clock input-source 1 External R0 e1 crc4
network-clock input-source 1 gigabitethernet 0/0
network-clock input-source 2 gigabitethernet 0/1
network-clock synchronization mode QL-enabled
no network-clock revertive

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