VLANs / Bridging / BPDU

From: Peter Wood (peter_at_alastria.net)
Date: 09/01/05

  • Next message: Peter Wood: "Re: VLANs / Bridging / BPDU" 
    Date: Thu, 01 Sep 2005 21:57:50 +0100
To: freebsd-net@freebsd.org

    Evening,

    I'm having an issue with using vlans and bridging. The issue is probably
    something that can be fixed in either FreeBSD or in the Cisco IOS.

    I'll explain what I have. I've got a external router that's sitting on
    vlan 20, also on 20 is a FreeBSD gateway which I intend to use as a
    firewall for the raw internet. The gateway also sits on 10 to pass the
    data to the machines protected by it.

    Or that was the plan anyway, a shortened (snipped media/mac) version of
    my ifconfig is as follows:

    raw0: flags=8842<BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
             status: active
             vlan: 20 parent interface: em0
    dmz0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
             inet 10.3.0.101 netmask 0xfff80000 broadcast 10.7.255.255
             status: active
             vlan: 10 parent interface: em0

    So the idea is raw0 (renamed vlan interface) accepts the traffic from
    the router, lets ipfw do it's work and then spits it back out via dmz0.
    As you can see both cloned vlan interfaces are on em0 on a 802.1Q trunk
    to a Cisco 2950.

    I am however having an issue with BPDU, the Cisco recognizes what it
    considers to be a loop in the topology. What I assume is that the Cisco
    is sending a BPDU packet out on VLAN10, the FreeBSD machine is passing
    that packet back out via VLAN20 (as I guess the bridge should), which
    the Cisco receives again, assumes a switch loop and blocks both of the
    vlan interfaces.

    Cisco errors are as follows:

    %SPANTREE-2-RECV_PVID_ERR: Received BPDU with inconsistent peer vlan id
    20 on GigabitEthernet0/1 VLAN10.
    %SPANTREE-2-BLOCK_PVID_PEER: Blocking GigabitEthernet0/1 on VLAN0020.
    Inconsistent peer vlan.
    %SPANTREE-2-BLOCK_PVID_LOCAL: Blocking GigabitEthernet0/1 on VLAN0010.
    Inconsistent local vlan.

    Now after writing this I'm thinking it's more a switch issue then a
    FreeBSD one, especially as the only other hit for the first Cisco
    message (apart from Cisco docs) is a thread for linux describing exactly
    the same problem with their bridging.

    Of which can be seen at:
    http://www.mail-archive.com/bridge@lists.osdl.org/msg00147.html

    However if anyone has any suggestions or has seen this issue, I'd be
    very greatful. Would it be possible to get the bridge to block BPDU
    (ugly hack I'm sure).

    Cheers,

    Pete. 

    -- 
Peter Wood BSc (Hons) :: <peter@alastria.net> :: Tel +44 1606 828010
_______________________________________________
freebsd-net@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-net
To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org"
  • Next message: Peter Wood: "Re: VLANs / Bridging / BPDU"

    Relevant Pages