ISL configuration on Cisco MDS

Assign hostname to switch

switchname <hostname>

Create Inter-Site Links (join two switches together to share zones)

conf t
trunk protocol enable #to enable trunking protocol
conf t
no trunk protocol enable #to disable trunking protocol

trunk protocol auto #to set trunking in auto mode . The preferred conf for CISCO MDS switches is (on) (auto) – one switch enabled, second is auto.

1. Connect 2 switches with FC cable on ANY port
2. In each switch, change port mode to TE:
show interface fc1/1
show running-config interface 1/1 # to see a current configuration
config t
interface fc1/1
switchport mode auto /on /off #will automatically set the port in TE mode in case it was previously set in another mode

3. Trunking ports should remain in VSAN1
4. Create new VSAN (same name and number) on both switches.
5. On both switches, run:
config t
interface fc1/1
switchport trunk allowed vsan 2-4 (To configure an allowed-active list of VSANs for an interface)
switchport trunk allowed vsan add 6 (Expands the specified VSAN 6 to the new allowed list)
no switchport trunk allowed vsan 2-4 (Disallow VSANS from being trunked)
no switchport trunk allowed vsan 5

One important note: you should create a VSANs BEFORE you allowing trunking on them –
otherwise trunking port will be automatically disabled due to VSAN mismatch.
Same problem can occur, if trunking interfaces are located in different VSANs
(for example, fc1/1 on switch A is in VSAN 2, while fc1/9 on switch B is in VSAN 3).


2 Replies to “ISL configuration on Cisco MDS”

  1. horribly written — you contradict your statements every line

    switchport mode auto /on /off #will automatically set the port in TE

    this isnt a command – its 3 different commands. so which sets the port mode in TE? auto? on? off?

    1. I get your point. Oftentimes these notes are primarily for my own benefit and can therefore be a very concise version of the steps included in the excellent documentation provided by Cisco themselves.
      In any case, if you’ll have issued the trunk protocol enable command shown at the start of this post, then when subsequently issuing the command switchport mode auto or switchport mode on then the port will automatically switch itself to TE mode. Hopefully you figured that out already.

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