VLAN trunking between Catlayst 3550-12T and 3Com switches

[kpap]

I am upgrading one customer LAN with one Cat 3550-12T, my client owns one 3Com 3900 and two 3Com 3300 switches. It is possible to create VLANs on the Catalyst 3550 and pass all the VLANs using 802.1Q to the 3Com hardware? I will route between VLANs on the Catalyst.

[bealedavid]

I believe that 802.1Q is a generic trunking protocol to pass VLAN information between switches...allowing you to trunk between Catalyst and say...ummmm...3Com switches :). You should be alright....

[rng4]

Depends on what you mean by "pass all the VLANs using 802.1Q to the 3com."

If "pass all the VLANs using 802.1Q to the 3com" means creating vlans on the 3550 and expect them to show up on the 3com, then it will not happen. 802.1Q is a trunking protocol. Cisco switches also run VTP, which is the protocol that carries VLAN information to all switches directly connected. VTP is Cisco proprietary and not supported on 3Com.

If "pass all the VLANs using 802.1Q to the 3com" means passing traffic as long as the same VLANs exist on the 3com, then it will work. Since the 3com does not support VTP, you'd have to manually create all VLANs on the 3com and make sure the VLAN numbers match. Once the VLANs are created on the 3com, and the port between the two swiches are set to trunk 802.1Q, you should be able to pass traffic. Make sure you set the port trunk mode to "on" and not "auto," "desirable," or "negotiate" as the 3Com supports non of this.