Help with network topology

Question

We have several old Cisco switches (currently only have VLAN 1 for everything). We are moving to a VOIP setup with Brocade and so I've (hopefully) configured the Brocade switch to handle the traffic correctly.

I've configured the Brocade with a default VLAN ID of 1, VLAN 10 for data/LAN traffic, VLAN 20 for our guest WIFI network, and VLAN 30 for VOIP. The phones should tag the packets for VLAN 30, the PC data should be untagged but come in as VLAN 10.

My question is: How can I get the old Cisco switch to take the VLAN 10 traffic and put it on it's default VLAN so that I don't have to create a VLAN 10 on two dozen Cisco switches that will be replaced soon anyway?

Answer 1

If you have no need to divide the traffic on all (and it does have to be all) the old hardware, then just make sure the switch connection from the old Cisco equipment connects to a VLAN 10 only port on your Brocade. Don't configure for trunking, tagging, or any management protocol on either side of that one link - Cisco will only tag if the port is configured for trunk. The Brocade will consider all the traffic that comes in from the old hardware to be VLAN 10 traffic, and your Ciscos will keep doing what they're doing thinking they are VLAN1 without any config changes.

This is not terribly good practice, so as soon anything changes this is a rather bad idea. If the replacement simply forges ahead as you describe however, it may be a way to tide you over.