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New Member

Changing VTP Setting and VLANs on CatOS

Greetings to all...

I'm working replacing our old 5505 Core switches running CatOS with 6509s running IOS with a new VLAN structure (VLAN 100 (5505) will be 400 (6509)). The down stream switches are 2948s running CatOS.

My problem is that everytime I either change SC0 or port 2/1 to the new VLAN, I lose my connectivity. Anyone know of a hot command that will change both at the same time?



New Member

Re: Changing VTP Setting and VLANs on CatOS

Have you considered using the console port to make the two changes sequentially?

New Member

Re: Changing VTP Setting and VLANs on CatOS

I would like to do it remotely... Some of these switches are not reachable easily...


Re: Changing VTP Setting and VLANs on CatOS

Do I understand that port 2/1 is the uplink port? If so, it should not be difficult. It is not necessary for the management and the trunk native VLAN to be the same, so your should be able to do them in sequence. In fact, I have just changed the management VLAN of our 20 Cat4000 CatOS switches remotely without any problem.

However, you will get cut off at the moment that you change the SC0, but this has nothing to do with the port 2/1 (assuming that the trunk is carrying both old and new management VLANs).

The way I did it was to start with the management station and all the switches on the old management VLAN. On your router (or L3 switch), create the new management VLAN, give its L3 interface a junk IP address, and enable ip proxy-arp on both old and new management VLANs. Note that the router is still routing the old management subnet, say, to the old management VLAN.

Now pick on an address which will be the router's IP address on the new management VLAN, say Go into your access switch, and configure that address as the default gateway, set ip route default Then reconfigure the SC0 interface to its new VLAN. At that point, your telnet session will get cut off because the management function of the 2948 is on the new VLAN. So, go to your router at set a host route for the access switch to the new VLAN, ip route VLAN400. You should now be able telnet to the switch from your management station. Packets from the management station to the switch will be routed by the host route. Packets from the switch to the management station will be routed courtesy of the proxy-arp.

Repeat this for each access switch, and once they are all done you can move your management station and give the router its proper address on the new VLAN. You can then remove the proxy ARP and/or change the native VLAN of the trunks at your leisure. If you are changing the native VLAN of the trunks, do the remote end first ;-).

Hope I have understood your question correctly, and hope this helps.

Kevin Dorrell