Clear configured allowed VSAN list on trunk ports of Cisco MDS

A friend asked a good question about how this command works on Cisco MDS FibreChannel switch: “switchport trunk allowed vsan all”.

To my surprise, I cannot find any specific official documents to explain it clearly. I did some experiment on one Cisco MDS 9148. And here is my conclusion.

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To clear whole allowed VSAN list and make every VSAN allowed at the same time, use “switchport trunk allowed vsan all” in the interface configuration mode.

To clear whole allowed VSAN list and make every VSAN NOT-allowed at the same time, use “no switchport trunk allowed vsan all”, in the interface configuration mode as well.

Otherwise, just use “switchport trunk allowed vsan” or “switchport trunk allowed vsan add” commands to edit the list of allowed VSAN list.


One more thing…

To edit the allowed VSAN list, remember to use “switchport trunk allowed vsan” command first before “switchport trunk allowed vsan add” commands.

On production network, remember to maintain the allowed VSAN list instead of allowing every new VSANs, just in case you created unnecessary VSANs by typing errors and they might have negative impacts on your MDS performance.