Question : VLAN Trunk Between Cisco 3550 Catalyst and 3Com 2948

Hello,

Has anyone had any luck setting up a trunk between a Cisco Catalyst L3 switch and a 3COM 2948 switch?  What I would like to achieve is to assign VLANs to ports on the 2948, so the hosts plugged into those ports will end up on the correct subnet according to what VLAN they are in and get a DHCP address from the correct pool.  

The DHCP part works fine as long as I have two separate 2948 switches plugged into two separate physical ports on the Catalyst (so I'm pretty sure that my VLANs and my DHCP server are both configured correctly), but I'm not having any luck separating a single 2948 switch into multiple VLANs.  I think this should be possible since both devices speak 802.1q.  

Can anyone verify whether this is possible or not, and if so, give me the steps to accomplish on both the Catalyst and the 3COM switches?  I'm essentially starting from a blank config on the Catalyst except for the VLANs I created.

Answer : VLAN Trunk Between Cisco 3550 Catalyst and 3Com 2948

Here is the configuration you should have, if for example you are trunking VLAN 1 and VLAN 2...

3COM:

On the trunk port, set VLAN 1 as an untagged member, and VLAN 2 as a tagged member.  Set all of the other ports as untagged members of the desired VLAN on that port.

Cisco:

Set the trunk port as follows:

switchport trunk encapsulation dot1q
switchport mode trunk
switchport trunk native vlan 1
switchport trunk allowed vlan 1,2
switchport nonegotiate


If that works for you, you should have no problems adding in additional vlans as needed.

Please let me know if you run into any problem getting this set up, and I can provide more details, but I'm pretty sure that'll work like a charm.