Trunking question - Cisco switches

Posted on 2009-04-28
Last Modified: 2012-05-06
I need some help with a trunking situation.  Let's say I have 3 switches (A, B, C) connected in series such that A<->B<->C so no loops or redundant links involved.  I have trunking configed on the links between the switches in very basic form (dot1q and all vlan's allowed).  On switch A and C there are VLANs 1 and 2 but switch B only has VLAN1.  All 3 switches are VTP transparent mode.  Why would I not be able to ping from something on VLAN2 on switch A to something on VLAN2 on switch C?  It seems that B is not passing traffic through for VLAN2.  Is this because B cannot pass traffic for a VLAN it's not config'd for or is it because A and C have set the root bridge for VLAN2 as themselves and as such will not try to send any VLAN2 traffic out any interfaces that are not local access ports in that VLAN?  Or is there something else going on?  
Question by:robbie_woodley
    LVL 9

    Accepted Solution

    You need to have the vlan on all switches ales the switch that dont have the VLAN will look at the packet and drop it due to invalid VLAN ID.
    LVL 3

    Expert Comment

    Are these switches participating in a VTP domain? Are there other switches connected to A, B and C? Have you considered creating a VTP domain, with one of your switches acting as a server and the other 2 in client mode? Let me know what you think and I'm happy to assist further.

    Otherwise, try Donboo's solution by adding VLAN 2 excatly the same way you did on switch A and C.

    I don't think this has anything to do with the bridge ID.

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