Chapter 14

Establishing a Frame 
Relay PVC Connection

© 1999, Cisco Systems, Inc.  14­1
© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­2
 Objectives

Upon completion of this chapter, you will
be able to perform the following tasks:
• Determine how Frame Relay operates
• Configure Frame Relay
• Configure Frame Relay subinterfaces
• Verify Frame Relay operation

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­3

 Frame Relay Overview
DCE or 
Frame
Relay Switch

CSU/DSU

Frame Relay works here.

• Virtual circuits make connections
• Connection­oriented service

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­4

 Frame Relay Stack

OSI Reference Model Frame Relay
Application

Presentation

Session
Transport
Network IP/IPX/AppleTalk, etc.
Data Link Frame Relay
EIA/TIA­232, 
Physical EIA/TIA­449, V.35, 
X.21, EIA/TIA­530

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­5

 Frame Relay Terminology

PVC
DLCI: 100
DLCI: 200
LMI
100=Active
400=Active

DLCI: 400
Local Access
Local Loop=64 kbps
Access
Loop=T1

PVC
Local Access
Loop=64 kbps
DLCI: 500

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­6

 Frame Relay 
Address Mapping
DLCI: 500 PVC 10.1.1.1
CSU/DSU

Inverse ARP or
Frame Relay map

Frame IP
DLCI (500)
Relay (10.1.1.1)

• Get locally significant DLCIs from provider 
• Map your network addresses to DLCIs
© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­7
 Frame Relay Signaling
DLCI: 500 PVC 10.1.1.1

x
CSU/DSU
LMI
500=Active DLCI: 400
400=Inactive PVC

Keepalive

Cisco supports three LMI standards:
• Cisco
• ANSI T1.617 Annex D
• ITU­T Q.933 Annex A
© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­8
 Frame Relay Inverse ARP and 
LMI Operation
1
Frame Relay
DLCI=100 Cloud DLCI=400

172.168.5.5 172.168.5.7

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­9

 Frame Relay Inverse ARP and 
LMI Operation
1
Frame Relay
DLCI=100 Cloud DLCI=400

172.168.5.5 172.168.5.7

Status Inquiry Status Inquiry
2 2

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­10

 Frame Relay Inverse ARP and 
LMI Operation
1
Frame Relay
DLCI=100 Cloud DLCI=400

172.168.5.5 172.168.5.7

Status Inquiry Status Inquiry
2 2

Local DLCI 100=Active Local DLCI 400=Active
3 34

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­11

 Frame Relay Inverse ARP and 
LMI Operation
1
Frame Relay
DLCI=100 Cloud DLCI=400

172.168.5.5 172.168.5.7

Status Inquiry Status Inquiry
2 2

Local DLCI 100=Active Local DLCI 400=Active
3 34

Hello, I am 172.168.5.5.
4

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­12

 Frame Relay Inverse ARP and 
LMI Operation (cont.)
Frame Relay
DLCI=100 Cloud DLCI=400

172.168.5.5 172.168.5.7

Frame Relay Map
5
172.168.5.5  DLCI  400  Active

Hello, I am 172.168.5.7.
4
Frame Relay Map
5
172.168.5.7  DLCI  100  Active

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­13

 Frame Relay Inverse ARP and 
LMI Operation (cont.)
Frame Relay
DLCI=100 Cloud DLCI=400

172.168.5.5 172.168.5.7

Frame Relay Map
5
172.168.5.5  DLCI  400  Active

Hello, I am 172.168.5.7.
4
Frame Relay Map
5
172.168.5.7  DLCI  100  Active
Hello, I am 172.168.5.5.
6

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­14

 Frame Relay Inverse ARP and 
LMI Operation (cont.)
Frame Relay
DLCI=100 Cloud DLCI=400

172.168.5.5 172.168.5.7

Frame Relay Map
5
172.168.5.5  DLCI  400  Active

Hello, I am 172.168.5.7.
4
Frame Relay Map
5
172.168.5.7  DLCI  100  Active
Hello, I am 172.168.5.5.
6
Keepalives Keepalives
7 7

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­15

 Configuring Basic Frame 
Relay
Rel. 11.2 Router Rel. 10.3 Router

HQ Branch

interface Serial1 interface Serial1

ip address 10.16.0.1 255.255.255.0 ip address 10.16.0.2 255.255.255.0
 
encapsulation frame-relay encapsulation frame-relay
bandwidth 64 bandwidth 64
frame-relay lmi-type ansi

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­16

 Configuring Basic Frame 
Relay (cont.)
Rel. 11.2 Router Rel. 10.3 Router

HQ Branch

interface Serial1 interface Serial1

ip address 10.16.0.1 255.255.255.0 ip address 10.16.0.2 255.255.255.0
 
encapsulation frame-relay encapsulation frame-relay
bandwidth 64 bandwidth 64
frame-relay lmi-type ansi

Inverse ARP
• Enabled by default
• Does not appear in configuration output
© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­17
 Configuring a Static Frame 
Relay Map
DLCI=110
IP address=10.16.0.1/24 

p1r1
HQ Branch
DLCI=100
IP address=10.16.0.2/24 

interface Serial1
ip address 10.16.0.1 255.255.255.0
encapsulation frame-relay
bandwidth 64
frame-relay map ip 10.16.0.2 110 broadcast

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­18

 Verifying Frame Relay 
Operation
Router#show interface s0
Serial0 is up, line protocol is up
Hardware is HD64570
Internet address is 10.140.1.2/24
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255/255, load 1/255
Encapsulation FRAME-RELAY, loopback not set, keepalive set (10 sec)
LMI enq sent 19, LMI stat recvd 20, LMI upd recvd 0, DTE LMI up
LMI enq recvd 0, LMI stat sent 0, LMI upd sent 0
LMI DLCI 1023 LMI type is CISCO frame relay DTE
FR SVC disabled, LAPF state down
Broadcast queue 0/64, broadcasts sent/dropped 8/0, interface broadcasts 5
Last input 00:00:02, output 00:00:02, output hang never
Last clearing of "show interface" counters never
Queueing strategy: fifo
Output queue 0/40, 0 drops; input queue 0/75, 0 drops
<Output omitted>

Displays line, protocol, DLCI, and LMI information

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­19

 Verifying Frame Relay 
Operation (cont.)

ame-relay lmi

for interface Serial0 (Frame Relay DTE) LMI TYPE = CISCO

bered info 0 Invalid Prot Disc 0
Call Ref 0 Invalid Msg Type 0
s Message 0 Invalid Lock Shift 0
mation ID 0 Invalid Report IE Len 0
t Request 0 Invalid Keep IE Len 0
q. Sent 113100 Num Status msgs Rcvd 113100
atus Rcvd 0 Num Status Timeouts 0

Displays LMI information

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­20

 Verifying Frame Relay 
Operation (cont.)
Router#show frame-relay pvc 100

PVC Statistics for interface Serial0 (Frame Relay DTE)

DLCI = 100, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0

input pkts 28 output pkts 10 in bytes 8398

out bytes 1198 dropped pkts 0 in FECN pkts 0
in BECN pkts 0 out FECN pkts 0 out BECN pkts 0
in DE pkts 0 out DE pkts 0
out bcast pkts 10 out bcast bytes 1198
pvc create time 00:03:46, last time pvc status changed 00:03:47

Displays PVC traffic statistics

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­21

 Verifying Frame Relay 
Operation (cont.)
how frame-relay map
(up): ip 10.140.1.1 dlci 100(0x64,0x1840), dynamic,
broadcast,, status defined, active

Displays the route maps, either static or dynamic

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­22

 Verifying Frame Relay 
Operation (cont.)

rame-relay map
ip 10.140.1.1 dlci 100(0x64,0x1840), dynamic,
broadcast,, status defined, active
frame-relay-inarp
me map

Clears dynamically created Frame Relay maps

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­23

 Verifying Frame Relay 
Operation (cont.)
debug Frame lmi
elay LMI debugging is on
ing all Frame Relay LMI data
erial0(out): StEnq, myseq 140, yourseen 139, DTE up
atagramstart = 0xE008EC, datagramsize = 13
R encap = 0xFCF10309
0 75 01 01 01 03 02 8C 8B
erial0(in): Status, myseq 140
T IE 1, length 1, type 1
A IE 3, length 2, yourseq 140, myseq 140
erial0(out): StEnq, myseq 141, yourseen 140, DTE up
atagramstart = 0xE008EC, datagramsize = 13
R encap = 0xFCF10309
0 75 01 01 01 03 02 8D 8C
erial0(in): Status, myseq 142
T IE 1, length 1, type 0
A IE 3, length 2, yourseq 142, myseq 142
VC IE 0x7 , length 0x6 , dlci 100, status 0x2 , bw 0

Displays LMI debug information

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­24

 Selecting a Frame Relay 
Topology

Full Mesh

Partial Mesh

Star (Hub and Spoke)

Frame Relay default: nonbroadcast, multiaccess (NMBA)
© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­25
 Reachability Issues with 
Routing Updates

B
Routing 1 B
Update
2
AA C
C

3
D

Problem:
Broadcast traffic must be replicated for 
each active connection

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­26

 Resolving Reachability Issues

Logical Interface  Physical
Interface Subnet A
S0.1 S0
S0.2 Subnet B
S0.3

Subnet C
Solution:
• Split horizon can cause problems in NBMA environments
• Subinterfaces can resolve split horizon issues
• A single physical interface simulates multiple logical interfaces

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­27

 Configuring Subinterfaces

• Point­to­Point
– Subinterfaces act as leased line 
– Each point­to­point subinterface requires its own 
subnet 
– Applicable to hub and spoke topologies 
• Multipoint
– Subinterfaces act as NBMA network so they do not 
resolve the split horizon issue
– Can save address space because uses single subnet
– Applicable to partial­mesh and full­mesh topology

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­28

 Configuring Point­to­Point 
Subinterfaces
10.17.0.1
s0.2 DLCI=110 10.17.0.2
A DL
s0.3 C
10.18.0.1 I=1 B
20
interface Serial0
no ip address
encapsulation frame-relay
! 10.18.0.2
interface Serial0.2 point-to-point
ip address 10.17.0.1 255.255.255.0
 bandwidth 64 C
frame-relay interface-dlci 110
!
interface Serial0.3 point-to-point
ip address 10.18.0.1 255.255.255.0
 bandwidth 64
frame-relay interface-dlci 120
!

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­29

 Multipoint Subinterfaces 
Configuration Example
= 120 B
DL C I
s2.2=10.17.0.1/24 s2.1=10.17.0.2/24
DLCI=130
RTR1
RTR3
DLCI=
140 s2.1=10.17.0.3/24

interface Serial2
no ip address RTR4
encapsulation frame-relay s2.1=10.17.0.4/24
!
interface Serial2.2 multipoint
ip address 10.17.0.1 255.255.255.0
 bandwidth 64
frame-relay map ip 10.17.0.2 120 broadcast
frame-relay map ip 10.17.0.3 130 broadcast
frame-relay map ip 10.17.0.4 140 broadcast

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­30

 Visual Objective
wg_pc_a
10.2.2.12
pod ro’s s0
e0/1 A 10.140.1.2
e0/2 e0 wg_ro_a B 10.140.2.2
10.2.2.3
s0 C 10.140.3.2
wg_sw_a 10.140.1.2/24
10.2.2.11 
D 10.140.4.2
E 10.140.5.2
PPP with CHAP F 10.140.6.2
wg_pc_l G 10.140.7.2
10.13.13.12 H 10.140.8.2
wg_ro_l I 10.140.9.2
PPP with CHAP
e0/1
e0/2 e0 s0 J 10.140.10.2
FR K 10.140.11.2
10.13.13.3  10.140.12.2/24
wg_sw_l L 10.140.12.2
10.13.13.11 

...

fa0/24 fa0/23 fa0/0 s2/7.x

10.140.1.1/24 … 10.140.12.1/24
core_ server   
core_sw_a core_ro
10.1.1.1 10.1.1.2 10.1.1.3

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­31

 Summary

After completing this chapter, you should
be able to perform the following tasks:
• Configure a Frame Relay PVC on a serial 
interface
• Configure Frame Relay subinterfaces
• Verify Frame Relay operation with show 
commands

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­32

 Review Questions

1.  What is a DLCI?
2. What are two methods to map a network 
layer address to a DLCI on a Cisco 
router?
3. What are the advantages of configuring 
Frame Relay subinterfaces?

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­33

 Blank for pagination

© 1999, Cisco Systems, Inc.  www.cisco.com ICND—14­34