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.