FWSM and dual chassis failover

Discussion in 'Cisco' started by jbracey, Jan 7, 2005.

  1. jbracey

    jbracey Guest

    Hello all:

    I've been trying to find out what the recommended bandwidth requirement
    for the failover link in a dual 6509 chassis setup with a FWSM in each.
    In the configuration guide for the FWSM 2.2 code, it mentions a 6 gig
    etherchannel between the chassis, but also says it's optional. The 2.3
    configuration guide makes no reference to how the link should be
    configured. Anybody have any sugesstions here?


    John Bracey, Network Analyst
    California State University, Chico
    jbracey, Jan 7, 2005
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  2. IMHO Cisco recommends a 6 GE channel because this is the same size the
    channel between MSFC/FWSM in a chassis has.

    In dual chassis failover setup, you may have a failover scenario that
    the primary FWSM fails but all other components in the primary chassis
    are running fine, including links to surrounding equipment (uplinks,
    DMZ connections etc) and the MSFC.

    In such a scenario, traffic routed/bridged to and from the FWSM flows
    through the failover channel or any other link between both chassis.


    More specific: Traffic flows over the links you trunk vlans that are
    assigned to the FWSM through vlan groups.

    Beside both FWSM specific failover connections (state replication and
    monitoring/testing traffic) the amount of your production traffic must
    be considered for capacity planning, too.

    Of course, you do not need to trunk FWSM production vlans through the
    FWSM failover trunk, you can have different trunks/links between both
    chassis for production traffic.

    I'd recommend a channel group that consists of GE links (from different
    Cat. modules) if possible.

    2 GE interfaces in that channel are more than enough if you trunk your
    production traffic through different links to the opposite chassis.

    If you want to use the FWSM failover trunk for production traffic link
    redundancy too, you must increase the amount of ports in that channel.

    Hope that helps,

    Christian Zeng, Jan 9, 2005
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  3. jbracey

    jbracey Guest


    Thanks for the info, yes this helps a bunch.

    -John Bracey
    jbracey, Jan 11, 2005
  4. jbracey

    d Guest

    Hi, just some additional information for you.

    We are running same scenario, we are using 2ge links between the boxes,
    the idea being that all traffic should flow through one device, if there
    is a failover then lowering the bandwidth is acceptable to us (but I think
    I might review this).

    However we have recently spent the last 5 months working with Cisco on a
    strange problem where traffic would not be forwarded properly. This
    problem turns out to be a problem with running etherchannels across two
    separate modules (line cards), even though Cisco knew about the problem it
    took over 5 months for them to tell us (we did have a work around to reset
    certain devices in a particular order). The problem is apparently
    hardware releated.

    So if you experience issues I recommend running the etherchannels on the
    same card.

    d, Jan 12, 2005
  5. jbracey


    Dec 17, 2007
    Likes Received:
    I'm wondering if you might have a Bug ID from Cisco?
    nyrocdan, Dec 17, 2007
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