Yesterday I noticed something strange when configuring a 2950 switch.
I had to create a new VLAN, so I went in to configuration mode and added a new vlan (interface) by entering “interface vlan 234″ and did a “no shutdown” on the interface. When I had done this I immediatly lost connection to the switch.
Then I remembered the 2950 switch can only have one IP adres at the time and it probably had been moved to the current active interface, which became 234. Thus I took my roll-over cable, logged on to the console and did a no shut on the vlan 1 interface to flip the IP address back to the VLAN 1 interface to correct the problem.
So I figured I mistaked the “interface vlan 234″ for the “vlan 234″ command and typed the ” vlan 234″ command in config mode. Strangely I again lost connection to the switch, allthough I did use the correct command this time.
After that I decided to try the depricated “vlan database” command. This time I did not loose connection to the switch and therefore I think using the vlan command in config mode automatically activates the vlan 234 interface. When the ”interface vlan 234″ has not been created the problem does not exist.