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c o m

C H A P T E R 8
Configuring and Managing VSANs

You can achieve higher security and greater stability in Fibre Channel fabrics by using virtual SANs
(VSANs). VSANs provide isolation among devices that are physically connected to the same fabric.
With VSANs you can create multiple logical SANs over a common physical infrastructure. Each VSAN
can contain up to 239 switches and has an independent address space which allows identical Fibre
Channel IDs (FCIDs) to be used simultaneously in different VSANs. VSANs offer the following
advantages:
• Traffic isolation—Traffic is contained within VSAN boundaries and devices reside only in one
VSAN ensuring absolute separation between user groups, if desired.
• Scalability—VSANs are overlaid on top of a single physical fabric. The ability to create several
logical VSAN layers increases the scalability of the SAN.
• Per VSAN fabric services—Replication of fabric services on a per VSAN basis provides increased
scalability and availability.
• Redundancy—Several VSANs created on the same physical SAN ensure redundancy. If one VSAN
fails, redundant protection is provided (to another VSAN in the same physical VSAN) by a
configured backup path between the host and the device.
• Ease of configuration—Users can be added, moved, or changed between VSANs without changing
the physical structure of a SAN. Moving a device from one VSAN to another only requires
configuration at the port level, not at a physical level.
This chapter includes the following sections:
• How VSANs Work, page 8-2
• VSANs Versus Zones, page 8-4
• Default and Isolated VSANs, page 8-6
• VSAN Membership, page 8-6
• VSAN Attributes, page 8-7
• Creating and Configuring VSANs, page 8-7
• Assigning VSAN Membership, page 8-8
• Deleting VSANs, page 8-9
• Viewing VSAN Configurations, page 8-10
• Default Settings, page 8-11

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How VSANs Work

A VSAN is a virtual storage area network (SAN). A SAN is a dedicated network that interconnects hosts
and storage devices primarily to exchange SCSI traffic. In SANs you use the physical links to make these
interconnections. A set of protocols run over the SAN to handle routing, naming, and zoning. You can
design multiple SANs with different topologies.
With the introduction of VSANs, the network administrator can build a single topology containing
switches, links, and one or more VSANs. Each VSAN in this topology has the same behavior and
property of a SAN. A VSAN has the following additional features:
• Multiple VSANs can share the same physical topology.
• The same Fibre Channel IDs (FCIDs) can be assigned to a host in another VSAN, thus increasing
VSAN scalability.
• Every instance of a VSAN runs all required protocols such as FSPF, domain manager, and zoning.
• Fabric-related configurations in one VSAN do not affect the associated traffic in another VSAN.
• Events causing traffic disruptions in one VSAN are contained within that VSAN and are not
propagated to other VSANs.
Figure 8-1 shows a fabric with three switches, one on each floor. The geographic location of the switches
and the attached devices is independent of their segmentation into logical VSANs. Within each VSAN,
all members can talk to one another. Between VSANs no communication is possible.

Figure 8-1 Logical VSAN Segmentation

Engineering Marketing Accounting

VSAN VSAN VSAN

Switch 1

Floor 3

Switch 2

Floor 2

Switch 3
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Figure 8-2 shows a physical Fibre Channel switching infrastructure with two defined VSANs: VSAN 2
(dashed) and VSAN 7 (solid). VSAN 2 includes hosts H1 and H2, application servers AS2 and AS3, and
storage arrays SA1 and SA4. VSAN 7 connects H3, AS1, SA2, and SA3.
As displayed in both Figure 8-2 and Figure 8-2, the switch icons indicate that these features apply to any
switch in the Cisco MDS 9000 family.

Figure 8-2 Example of two VSANs

H2 H3 AS1 AS2 AS3

H1

FC FC FC FC

SA1 SA2 SA3 SA4

Link in VSAN 2
Link in VSAN 7
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Trunk link

The four switches in this network are interconnected by trunk links that carry both VSAN 2 and VSAN
7 traffic. Thus the inter-switch topology of both VSAN 2 and VSAN 7 are identical. This is not a
requirement and a network administrator can enable certain VSANs on certain links to create different
VSAN topologies.
Without VSANs, a network administrator would need separate switches and links for separate SANs. By
enabling VSANs, the same switches and links may be shared by multiple VSANs. VSANs allow SANs
to be built on port granularity instead of switch granularity. Figure 8-2 illustrates that a VSAN is a group
of hosts or storage devices that communicate with each other using a virtual topology defined on the
physical SAN.
The criteria for creating such groups differ based on the VSAN topology:
• VSANs can separate traffic based on the following requirements:
– Different customers in storage provider data centers
– Production or test in an enterprise network
– Low and high security requirements
– Backup traffic on separate VSANs
– Replicating data from user traffic

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• VSANs can meet the needs of a particular department or application.

VSANs Versus Zones

You can define multiple zones in a VSAN. Because two VSANs are equivalent to two nonconnected
SANs, zone A on VSAN 1 is different and separate from zone A in VSAN 2. Table 8-1 lists the
differences between VSANs and zones.

Table 8-1 VSAN and Zone Comparison

VSANs Zones
VSANs equal SANs with routing, naming, and zoning protocols. These protocols are not available on a per-zone basis.
— Zones are always contained within a VSAN. Zones never
span two VSANs.
VSANs limit unicast, multicast, and broadcast traffic. Zones limit unicast traffic.
Membership is typically defined using the VSAN ID to Fx ports. Membership is typically defined by the pWWN.
An HBA or a storage device may belong only to a single An HBA or storage device can belong to multiple zones.
VSAN—the VSAN associated with the Fx port.
VSANs enforce membership at each E port, source port, and Zones enforce membership only at the source and
destination port. destination ports.
VSANs are defined for larger environments (storage service Zones are defined for a set of initiators and targets not
providers). visible outside the zone.
VSANs encompass the entire fabric. Zones are configured at the fabric edge.

Figure 8-3 shows the possible relationships between VSANs and zones. In VSAN 2, three zones are
defined: zone A, zone B, and zone C. Zone C overlaps both zone A and zone B as permitted by Fibre
Channel standards. In VSAN 7, two zones are defined: zone A and zone D. No zone crosses the VSAN
boundary—they are completely contained within the VSAN. Zone A defined in VSAN 2 is different and
separate from zone A defined in VSAN 7.

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Figure 8-3 VSANS with Zoning

Physical Topology

AS2 AS3
Zone A
H2 SA1
VSAN 2
Zone C

H1 SA4
Zone B

H3
Zone D
VSAN 7
Zone A
AS1 SA2 SA3

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Default and Isolated VSANs

Up to 256 VSANs can be configured in a switch. Of these, one is a default VSAN (VSAN 1), and another
is an isolated VSAN (VSAN 4094). User-specified VSAN IDs range from 2 to 4093.

Default VSANs
The factory settings for switches in the Cisco MDS 9000 Family have only the default VSAN 1 enabled.
If you do not need more than one VSAN for a switch, use this default VSAN as the implicit parameter
during configuration. If no VSANs are configured, all devices in the fabric are considered part of the
default VSAN. By default, all ports are assigned to the default VSAN.

Note VSAN 1 cannot be deleted. It can be suspended.

Isolated VSANs
VSAN 4094 is an isolated VSAN. All non-trunking ports are transferred to this VSAN when the VSAN
to which they belong is deleted. This avoids an implicit transfer of ports to the default VSAN or to
another configured VSAN. All ports in the deleted VSAN are isolated (disabled).

Note When you configure a port in VSAN 4094 or move a port to VSAN 4094, that port is immediately
isolated.

Caution Do not use an isolated VSAN to configure ports.

The show vsan 4094 membership command displays all ports associated with the isolated VSAN.

VSAN Membership
Port VSAN membership on the switch is assigned on a port-by-port basis.
By default each port belongs to the default VSAN. You can change the VSAN membership by using the
vsan number interface type port/slot command.
Trunking ports have an associated list of VSANs that are part of an allowed list (see Chapter 10,
“Configuring Trunking”).

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VSAN Attributes
VSANs have the following attributes:
• VSAN ID—The VSAN ID identifies the VSAN as the default VSAN (VSAN 1), user-defined
VSANs (VSAN 2 to 4093), and the isolated VSAN (VSAN 4094).
• State—The administrative state of a VSAN can be configured to an active (default) or suspended
state. Once VSANs are created, they may exist in various conditions or states.
– The active state of a VSAN indicates that the VSAN is configured and enabled. By enabling a
VSAN, you activate the services for that VSAN.
– The suspended state of a VSAN indicates that the VSAN is configured but not enabled. If a port
is configured in this VSAN, it is disabled. Use this state to deactivate a VSAN without loosing
the VSAN’s configuration. All ports in a suspended VSAN are disabled. By suspending a
VSAN, you can preconfigure all the VSAN parameters for the whole fabric and activate the
VSAN immediately.
• VSAN name—This text string identifies the VSAN for management purposes. The name can be
from 1 to 32 characters long and it must be unique across all VSANs. By default, the VSAN name
is a concatenation of VSAN and a four-digit string representing the VSAN ID. For example, the
default name for VSAN 3 is VSAN0003.

Note A VSAN name must be unique.

• Load balancing attributes—These attributes indicate the use of the source-destination ID (src-dst-id)
or the originator exchange OX ID (src-dst-ox-id, the default) for load balancing path selection.

Operational State of a VSAN

A VSAN is in the operational state if the VSAN is active and at least one port is up. This state indicates
that traffic can pass through this VSAN. This state cannot be configured.

Creating and Configuring VSANs

You cannot configure any application-specific parameters for a VSAN before creating the VSAN.
To create and configure VSANs, follow these steps:

Command Purpose
Step 1 switch# config t Enters configuration mode.
Step 2 switch(config)# vsan database Configures the database for a VSAN. Application
switch(config-vsan-db)# specific VSAN parameters cannot be configured
from this prompt.
Step 3 switch(config-vsan-db)# vsan 2 Creates a VSAN with the specified ID (2) if that
switch(config-vsan-db)# VSAN does not exist already.
Step 4 switch(config-vsan-db)# vsan 2 name TechDoc Updates the VSAN with the assigned name
updated vsan 2 (TechDoc).
switch(config-vsan-db)#

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Command Purpose
Step 5 switch(config-vsan-db)# vsan 2 Enables the load balancing guarantee for the
loadbalancing src-dst-id selected VSAN and directs the switch to use the
switch(config-vsan-db)#
source and destination ID for its path selection
process.
Step 6 switch(config-vsan-db)# no vsan 2 Negates the command issued in the previous step
loadbalancing src-dst-id and reverts to the default values of the
switch(config-vsan-db)#
load-balancing parameters.
Step 7 switch(config-vsan-db)# vsan 2 Changes the path selection setting to use the source
loadbalancing src-dst-ox-id ID, the destination ID, and the OX ID (default).
switch(config-vsan-db)#
Step 8 switch(config-vsan-db)# vsan 2 suspend Suspends the selected VSAN.
switch(config-vsan-db)#
Step 9 switch(config-vsan-db)# no vsan 2 suspend Negates the suspend command issued in the
vs.-config-vsan-db# previous step.
Step 10 switch(config-vsan-db)# end Returns you to EXEC mode.
switch#

Assigning VSAN Membership

To assign VSAN membership, follow these steps:

Command Purpose
Step 1 switch# config t Enters configuration mode.
Step 2 switch(config)# vsan database Configures the database for a VSAN.
switch(config-vsan-db)#
Step 3 switch(config-vsan-db)# vsan 2 Creates a VSAN with the specified ID (2) if
switch(config-vsan-db)# that VSAN does not exist already.
Step 4 switch(config-vsan-db)# vsan 2 interface fc1/8 Assigns the membership of the fc1/8 interface
switch(config-vsan-db)# to the specified VSAN (VSAN 2).
Step 5 switch(config-vsan-db)# vsan 7 Creates another VSAN with the specified ID
switch(config-vsan-db)# (7) if that VSAN does not exist already.
Step 6 switch(config-vsan-db)# vsan 7 interface fc1/8 Updates the membership information of the
switch(config-vsan-db)# interface to reflect the changed VSAN.

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Deleting VSANs
When an active VSAN is deleted, all of its attributes are removed from the running configuration.
VSAN related information is maintained by the system software.
• VSAN attributes and port membership details are maintained by VSAN manager. This feature is
affected when you delete a VSAN from the configuration. When a VSAN is deleted all the ports in
that VSAN are made inactive and the ports are moved to the isolated VSAN. If the same VSAN is
recreated, the ports do not automatically get assigned to that VSAN. You must explicitly reconfigure
the port VSAN membership (see Figure 8-4).

Figure 8-4 VSAN Port Membership Details

Before After
Default VSAN 7 Default VSAN 7
VSAN VSAN
fc1/1 fc1/3 fc1/1 fc1/3
fc1/2 fc1/4 fc1/2 fc1/4

Isolated VSAN 12 Isolated VSAN 12

VSAN VSAN

fc1/5 fc1/5 fc1/5

fc1/6 fc1/6 fc1/6

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Switch 1 Switch 1

• VSAN-based runtime (name server), zoning, and configuration (static routes) information is
removed when the VSAN is deleted.
• Configured VSAN interface information is removed when the VSAN is deleted.

Note The allowed VSAN list is not affected when a VSAN is deleted (see Chapter 10, “Configuring
Trunking”).

Any commands for a nonconfigured VSAN are rejected. For example, if VSAN 10 is not configured in
the system, then a command request to move a port to VSAN 10 is rejected.
To delete a VSAN and its various attributes, follow these steps:

Command Purpose
Step 1 switch# config t Enters configuration mode.
Step 2 switch(config)# vsan database Configures the VSAN database.
switch(config-db)#
Step 3 switch-config-db# vsan 2 Places you in VSAN configuration mode.
switch(config-vsan-db)#
Step 4 switch(config-vsan-db)# no vsan 5 Deletes VSAN 5 from the database and switch.
switch(config-vsan-db)#
Step 5 switch(config-vsan-db)# end Places you in EXEC mode.
switch#

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Viewing VSAN Configurations

Use the show vsan command to display information about configured VSANs (see Examples 8-1 to 8-6).

Example 8-1 Displays the Configuration for a Specific VSAN

switch# show vsan 100

vsan 100 information
name:VSAN0100 state:active
in-order guarantee:no interoperability mode:no
loadbalancing:src-id/dst-id/oxid

Example 8-2 Displays the VSAN Usage

switch# show vsan usage

4 vsan configured
configured vsans:1-4
vsans available for configuration:5-4093

Example 8-3 Displays All VSANs

switch# show vsan

vsan 1 information
name:VSAN0001 state:active
in-order guarantee:no interoperability mode:no
loadbalancing:src-id/dst-id/oxid
vsan 2 information
name:VSAN0002 state:active
in-order guarantee:no interoperability mode:no
loadbalancing:src-id/dst-id/oxid
vsan 7 information
name:VSAN0007 state:active
in-order guarantee:no interoperability mode:no
loadbalancing:src-id/dst-id/oxid
vsan 100 information
name:VSAN0100 state:active
in-order guarantee:no interoperability mode:no
loadbalancing:src-id/dst-id/oxid
vsan 4094:isolated vsan

Example 8-4 Displays Membership Information for the Specified VSAN

switch # show vsan 1 membership

vsan 1 interfaces:
fc1/1 fc1/2 fc1/3 fc1/4 fc1/5 fc1/6 fc1/7 fc1/9
fc1/10 fc1/11 fc1/12 fc1/13 fc1/14 fc1/15 fc1/16 port-channel 99

Note Interface information is not displayed if interfaces are not configured on this VSAN.

Example 8-5 Displays Membership Information for All VSANs

switch # show vsan membership

vsan 1 interfaces:
fc2/16 fc2/15 fc2/14 fc2/13 fc2/12 fc2/11 fc2/10 fc2/9
fc2/8 fc2/7 fc2/6 fc2/5 fc2/4 fc2/3 fc2/2 fc2/1
fc1/16 fc1/15 fc1/14 fc1/13 fc1/12 fc1/11 fc1/10 fc1/9
fc1/7 fc1/6 fc1/5 fc1/4 fc1/3 fc1/2 fc1/1
vsan 2 interfaces:

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vsan 7 interfaces:
fc1/8
vsan 100 interfaces:
vsan 4094(isolated vsan) interfaces:

Example 8-6 Displays Membership Information for a Specified Interface

switch # show vsan membership interface fc1/1

fc1/1
vsan:1
allowed list:1-4093

Default Settings
Table 8-2 lists the default settings for all configured VSANs.

Table 8-2 Default VSAN Parameters

Parameters Default
State Active state.
Name Concatenation of VSAN and a four-digit string representing the
VSAN ID. For example, VSAN 3 is VSAN0003.
Load-balancing attribute OX ID (src-dst-ox-id).
Port membership Default VSAN (VSAN 1).

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