These range from 1-4094. VSAN 1 can't be used (it includes all ports and is used for mangement) neither can 4094 (isolated VSAN into which orphaned ports are assigned). Each VSAN gets a domain ID. For AIX and HP-UX, static assignement should be used i,e. persists across reboots.

Cisco Fabric Services

These distribute application configs between switches. Normally, at least the following would be running; Fabric Startup Configuration (FSCM) , Inter VSAN Routing (IVR) and dev-alias enabled. The following commands can be used to check services:

 show cfs application
 show cfs peers  (which switches will share)

If FSCM is CFS enabled, when the config is saved it will be saved across the fabric. To save the config run:

 copy running-config startup-config fabric

Standard vs Enhanced Device Aliases

  • Standard - The switch substitutes the WWN for the dev alias and passes this to the app being configured, e.g. IVR. If the dev alias is updated, e.g. after an HBA failure, the WWN is NOT passed to the app. To update the services affected, the device needs to be removed, devalias updated and then re-added to the service.
  • Enhanced - The alias, not the WWN, is passed to the app/service and therefore any WWN changes are automatically passed to the relevant app/service.


A 24 port module consists of 4 groups of 6 ports. For 4Gb switches, each group has a maximum throughput of 12.8Gb to the crossbar, i.e. not all ports can run a 4Gb. For example, 3 ports could run at 4GB but the remaining 3 ports would have 1Gb between them

Oversubscription Options

Strict Oversubscription means that the port speeds are enforced, e.g. all set to 2Gb. Unlimited Oversubscription is more flexible, for example, 3 ports could be set to 4Gb to ensure they always get the throughput whilst the others could be set to 4Gb shared, so they could use the unused bandwidth from the dedicated commands.

Load Balancing ISLs

Can choose Source_ID, Dest_ID or S_ID, D_ID, 0X_ID. S_ID, D_ID means that the link used for the first exchange will be used for all subsequent exchanges. However, S_ID, D_ID, 0x_ID means that the link selected will be used for all frames of that exchange but the next exchange could be on a different link. S_ID, D_ID, 0x_ID is preferable but some links, e.g.for HP EVA, require S_ID, D_ID .

Some useful Commands

  • show fcns database - show name server
  • show zoneset - show zones & IVRs
  • show flogi database - show fabric logins
  • show port-resources module n - show port speeds
  • show vsan x membership - which ports are in vsan x
  • show int fc1/1 - show port status

To enable a port

 conf t
 interface fc1/1,fc1/2
 no shut
  • show license host-id - display serial number
  • show wwn switch - show switch WWN
  • show interface mgmt0 - show IP address of switch
  • show ip route - show default gateway

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