I tried to remove a legacy vlan from a particular port channel when I was working on a clean up project for "vlan 12" . This vlan was configured through the port channel between 2 switches. One switch was the MDF distribution switch(SW A) and another IDF distibution switch (SW B). Port 25 and 26 (both ends) was bundled to the port channel (po1).
When i initiated the command for port 25 on SW B e.g. " switchport trunk allowed vlan 10,11" removing vlan 12, I was no longer accessible to it. The session got me kicked out and i was no longer able to ping i. I was then disconnected to it and switch might have been hung. I'm not sure what exactly caused the issue but I feel I should have unbundled the port from the port channel before removing vlan 12 from each individual port.
What i suspect was a vlan negotiation problem wihtin the port channel. Is that we need to unbundle the port channel, then, remove the vlan from it and move forward to remove from each individual port? I havent tested this on a lab and would like an advice for anybody face a similar issue.
Was your management done via Vlan12? If so...that would be a problem.
Ideally if you want to remove a VLAN from a port channel, you remove it from the port channel interface. This will then propogate down to the physical interfaces.
If you remove it from the physical interfaces first, your port configurations will no longer match the port channel interface configuration, and the ports will be unbundled. Typically this results in one going into blocking via spanning tree.
VLAN 12 was not the management vlan. It just was an old vlan that needs to be removed. VLAN 2 was the manegement vlan and was configured on the trunk. I believe your second point should be a valid reason for it. I should have removed it on the port channel before moving to the individual ports.