Cisco Nexus 5000 Series NX-OS Software Configuration Guide

VSAN 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 operation 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 (FC IDs) can be assigned to a host in another VSAN, which increases 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 1-1 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. No communication between VSANs is possible. Within each VSAN, all members can talk to one another.

Figure 1-1 Logical VSAN Segmentation

Figure 1-2 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 application servers or storage arrays can be connected to the switch using Fibre Channel or virtual Fibre Channel interfaces. A VSAN can include a mixture of Fibre Channel and virtual Fibre Channel interfaces.

Figure 1-2 Example of Two VSANs

The four switches in this network are interconnected by VSAN trunk links that carry both VSAN 2 and
VSAN 7 traffic. You can configure a different inter-switch topology for each VSAN. In Figure 1-2, the inter-switch topology is identical for VSAN 2 and VSAN 7.

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 1-2 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

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

VSAN Advantages

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 (to another VSAN in the same physical SAN) is configured using a 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.

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.

VSANs Versus Zones

Zones are always contained within a VSAN. You can define multiple zones in a VSAN.

Because two VSANs are equivalent to two unconnected SANs, zone A on VSAN 1 is different and separate from zone A in VSAN 2. Table 1-1 lists the differences between VSANs and zones.

Figure 1-3 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. Zone A defined in VSAN 2 is different and separate from zone A defined in VSAN 7.

Figure 1-3 VSANS with Zoning

About VSAN Creation

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 VSANs Statically

You cannot configure any application-specific parameters for a VSAN before creating the VSAN.

To create VSANs, perform this task:

About Port 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 assign VSAN membership to ports using one of two methods:

• Statically—Assigning VSANs to ports.

See the “Assigning Static Port VSAN Membership” section.

• Dynamically—Assigning VSANs based on the device WWN. This method is referred to as dynamic port VSAN membership (DPVM). Cisco Nexus 5000 Series switches do not support DPVM.

VSAN trunking ports have an associated list of VSANs that are part of an allowed list (see Chapter 1, “Configuring VSAN Trunking”).

Assigning Static Port VSAN Membership

To statically assign VSAN membership for an interface port, perform this task:

Displaying VSAN Static Membership

To display the VSAN static membership information, use the show vsan membership command.

The following example displays membership information for the specified VSAN:

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

The following example displays membership information for all VSANs:

The following example displays static membership information for the specified interface:

About the Default VSAN

The factory settings for switches in the Cisco Nexus 5000 Series have only the default VSAN 1 enabled. We recommend that you do not use VSAN 1 as your production environment VSAN. 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, but it can be suspended.

Note 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.

About the Isolated VSAN

VSAN 4094 is an isolated VSAN. When a VSAN is deleted, all nontrunking ports are transferred to the isolated VSAN to avoid an implicit transfer of ports to the default VSAN or to another configured VSAN. This action ensures that all ports in the deleted VSAN become 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.

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Note 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.

Displaying Isolated VSAN Membership

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

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.

About Static VSAN Deletion

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 as follows:

• VSAN attributes and port membership details are maintained by the 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 1-4).

Figure 1-4 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.

Note The allowed VSAN list is not affected when a VSAN is deleted (see Chapter 1, “Configuring VSAN 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.

Deleting Static VSANs

To delete a VSAN and its various attributes, perform this task:

About Load Balancing

Load-balancing 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.

Configuring Load Balancing

To configure load balancing on an existing VSAN, perform this task:

About Interop Mode

Interoperability enables the products of multiple vendors to connect with each other. Fibre Channel standards guide vendors to create common external Fibre Channel interfaces. For additional information, see the “Switch Interoperability” section.