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Adding a VLAN to a trunk for a WiSM1 question

I came across something today I thought was a bit odd.  When adding a VLAN to a trunk in a core switch for the WiSM module, the command is slightly different than the usual “add” command.

The following two commands:

wism module 2 controller 1 allowed-vlan 2347

wism module 2 controller 2 allowed-vlan 2347

Result in the following configuration.  There’s no “add”…

wism module 2 controller 1 allowed-vlan 101,102,778,2347

wism module 2 controller 2 allowed-vlan 101,102,778,2347


Here’s the lack of “add”…

My_Core_Switch(config)#wism module 2 controller 1 allowed-vlan ?

  WORD  vlan range 1-1001,1006-4094


What I found strange was the fact that issuing the command for wism module 2 controller 1 (to add VLAN 2347) on the switch resulted in a missed ping  from my workstation  to the management IP of the controller.  Before making this change, I started a continuous ping from my wired workstation to the WLAN controller.  This has never been the case when using the normal “add” command when adding a VLAN to a trunk to a 4404 or 5508 WLAN controller.

The problem is when entering the command for the second module  "wism module 2 controller 2 allowed-vlan 2347".   The second module lost 25 of the continuous pings.  I was able to replicate this on the backup WiSM farm.  Same exact behavior.  My test workstation on Wi-Fi lost connectivity for almost two minutes.  I assume the trunk to the WLAN controller went down.

I didn’t see anything in the switch's logs about the interface going up and down in the switch.  However, I did look at the logs in the WLAN controller and it showed that it definitely took the trunk down for 90 seconds or so – depending how you look at the traps and interpret them.