Propagating Vlan info between Cisco and non Cisco switches

Unanswered Question


I have a Cisco Switch which is a VTP server where I create all Vlans. I want to propagate this Vlan info to non Cisco devices (Nortel). I have configured dot1q as Trunking protocol ports connecting between these two Switches . Do I need to configure any more settings to propagate all the Vlan info from Cisco to Non Cisco ?



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aijaz802 Wed, 02/13/2008 - 04:13

Hi Raju,

VTP is Cisco proprietary protocol, I think you can't propagate these vlans across the trunks using VTP.

You should also create the vlans on nortel switches also.

Rate if it helps...



Goutam Sanyal Wed, 02/13/2008 - 05:09


As per Cisco

1. In a network of Cisco switches connected through 802.1Q trunks, the switches maintain one instance of spanning tree for each VLAN allowed on the trunks. Non-Cisco 802.1Q switches maintain only one instance of spanning tree for all VLANs allowed on the trunks.

When you connect a Cisco switch to a non-Cisco device through an 802.1Q trunk, the Cisco switch combines the spanning tree instance of the native VLAN of the trunk with the spanning tree instance of the non-Cisco 802.1Q switch. However, spanning tree information for each VLAN is maintained by Cisco switches separated by a cloud of non-Cisco 802.1Q switches. The non-Cisco 802.1Q cloud separating the Cisco switches is treated as a single trunk link between the switches.

2. Make sure the native VLAN for an 802.1Q trunk is the same on both ends of the trunk link. If the VLAN on one end of the trunk is different from the VLAN on the other end, spanning tree loops might result.

3. Disabling spanning tree on any VLAN of an 802.1Q trunk can cause spanning tree loops.

Hope it'll help u!!!



Pls rate if it hepls!!!

aijaz802 Wed, 02/13/2008 - 05:31


I think on Cisco switch and nortel you have created the trunk ports and able to communicate.

To pass vlans of nortel you need to do like this..

set vlan 2 name newvlan

set vlan 2 port 8 tag 2 [port 8 is trunk port connected to cisco]



Goutam Sanyal Wed, 02/13/2008 - 04:22

Hi Raju,

when VTP is the proprietary of Cisco then you have to put same to Non-Cisco also.



clifton.howell Wed, 02/13/2008 - 06:10


Aijaz is correct in that other switches don't understand the Cisco VTP so they discard the packets. I don't know a lot about Nortel switches but I had a similar experience with an HP switch integrating with our Cisco network. Both switches were setup with Rapid STP and dot1Q trunks but since the HP switch doesn't understand VTP we had to manually create the VLANs we wanted and we also pruned off the VLANs we weren't using from the trunk link.



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