External Transparent Bridge between two VLANs

Discussion in 'Cisco' started by lyle, Aug 10, 2005.

  1. lyle

    lyle Guest

    Good Morning,

    I have recently run into a problem when trying to recable our network
    to utilize a managed catalyst switch as a distribution switch. Our
    current network looks like this:

    WAN Link -> Catalyst (VLAN 2) -> Router -> Catalyst (VLAN 3) ->
    Transparent Bridge with Firewall -> Dumb Switch -> Rest of switches

    Basically The WAN and External Router Card are on one VLAN on the
    switch, the Internal Router Card and External Transparent Bridge port
    are on another, and then the Internal port of the bridge goes to a 24
    port unmanaged switch that then feeds the rest of our access switches.

    The plan is to use another VLAN on the catalyst to distribute to the
    rest of the switches. The final goal would have the Internal port on
    the Bridge going to the catalyst on VLAN 4, and the rest of the
    switches all linked to over VLAN 4 as well.

    So I tried that, and this is what happened... The external interface
    of the bridge was in VLAN 3 on port 8, the internal interface was in
    VLAN 4 on port 15. For approximately 1 minute the network stayed up
    with no problem, then suddenly we lost external access, but
    communication was still working between racks. Looking on the switch
    it showed the two firewall ports to be up, but they had dropped out of
    their VLANs. Running "sh vlan brief" showed that they did not exist in
    any VLAN at all. Im guessing that the switch assumed there was a
    network loop, I need to know how to tell it to ignore that and continue
    on as usual...

    Any ideas? Has anyone gotten something like this to work?
    lyle, Aug 10, 2005
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