Table Of Contents

Configuring and Managing VSANs

How VSANs Work

VSANs Versus Zones

Default and Isolated VSANs

Default VSANs

Isolated VSANs

VSAN Membership

VSAN Attributes

Operational State of a VSAN

Adding and Configuring VSANs

Deleting VSANs

Default Settings

Configuring and Managing VSANs

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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 SAN) 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 contains the following topics:

•How VSANs Work

•VSANs Versus Zones

•Default and Isolated VSANs

•VSAN Membership

•VSAN Attributes

•Adding and Configuring VSANs

•Deleting VSANs

•Default Settings

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 11-1 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 11-1 Logical VSAN Segmentation

Figure 11-2 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.

The switch icons shown in both figures indicate that these features apply to any switch in the Cisco MDS 9000 family.

Figure 11-2 Example of Two VSANs

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. 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

•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 11-1 lists the differences between VSANs and zones.

Table 11-1 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 VSAN--the VSAN associated with the Fx port.	An HBA or storage device can belong to multiple zones.
VSANs enforce membership at each E port, source port, and destination port.	Zones enforce membership only at the source and destination ports.
VSANs are defined for larger environments (storage service providers).	Zones are defined for a set of initiators and targets not visible outside the zone.
VSANs encompass the entire fabric.	Zones are configured at the fabric edge.

Figure 11-3 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.

Figure 11-3 VSANS with Zoning

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.

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

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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).

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

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Caution Do not use an isolated VSAN to configure ports.

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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.

Trunking ports have an associated list of VSANs that are part of an allowed list.

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 losing 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.

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Note A VSAN name must be unique.

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•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.

Adding and Configuring VSANs

To add and configure VSANs, perform the following steps.

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Step 1 From the Fabric Manager menu tree in the Logical pane, click on the desired VSAN, or from Device Manager, choose FC > VSAN, or click the VSAN icon on the toolbar.

The Fabric Manager's Information pane displays VSAN attributes for multiple switches. The VSAN dialog box in the Device Manager displays VSAN general attributes for a single switch.

Step 2 From Fabric Manager, click Create VSAN, or from Device Manager, click Create.

You see the Create dialog box.

Step 3 Complete the fields on this dialog box and click Create to add the 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.

Figure 11-4 VSAN Port Membership Details

•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.

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Note The allowed VSAN list is not affected when a VSAN is deleted.

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Default Settings

The table below lists the default settings for all configured VSANs.

Table 11-2 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).