I had an issue where a new Cisco switch changed the vlans of other switches to vlan 1 (which was shut down) when plugged in. I was going to use our management vlan to update the IOS and plugged into a trunk port from an access port with only the management vlan.
Details about the Cisco switch
Port 1 trunk
vlans with IP management
default route to the core
vtp transparent, no domain, no password
I plugged into an access port with the management vlan untagged (default) on an Extreme switch. A saw a BPDU broadcast, complaint about vlan mismatch, and then nodes started to drop.
This only affected other switches that were Cisco by changing the channel-group port(s) vlan to default vlan 1 which is shut down. When the switch was restarted it loaded the startup config and all was well.
Basically I want to know what needs to be done so I don't repeat the adventure.