Question : VLANS from 3COM to CISCO via Trunk Port

Hi,
I am having a bit of a problem

Currently I have a 3COM core switch hosting a number of VLANs. These are for various subnets for printers, workstations, servers etc.

All of these vlans are trunked through to a cisco switch (various) using 3COM's trunk port and vlan tagging.

Last night I created two new VLANs on the 3COM switch, and configured my ESX server (which is plugged into one of the cisco switch'es trunking ports) to use this VLAN.

Nothing worked. I was unable to see in ESX that the network adapter observed this new VLAN with its assocaiated IP addreses and I was unable to ping the new VLAN's interface IP address from the cisco switch.

It's almost as if the 3COM switch isn't tagging any of the trunk traffic with this new VLAN, even though the trunk is configured to pass all vlans.

I have gone crazy looking for a reason. All existing VLANs are being passed through the trunk ports into the cisco switches without problem. It's almost like it's not thinking it needs to. The 3COM model is a 5500 series, so there are not too many options. We are using Link Agreegation between the 3COM and the CISCO but that shouldn't make any difference..

Any ideas?

Answer : VLANS from 3COM to CISCO via Trunk Port

Are the Cisco switches on your network set to vtp mode client or transparent?  If you type "sh vlan brief" on the Cisco's, do you see the new VLAN?  You may need to create the VLAN's on the Cisco switches if they are not accepting new VLAN ID's.

See this - http://en.wikipedia.org/wiki/VLAN_Trunking_Protocol