port channel, CatOS, unidirectional links... the usual suspects

Discussion in 'Cisco' started by HCE, Sep 11, 2006.

  1. HCE

    HCE Guest

    The Scenario:

    Two 6500's. Three of the gig links between them configured as a port
channel.  All three are trunks.  CatOS (grrrr...)

    The issue:

    Users start complaining.  I isolate the problem to this pair of cats
and take a look.  CPU at 100...  interfaces dropping millions of
packets...I look at the logs...  HSRP is reporting dup addresses on
gob of segments....  lots of them...  as many as you might find,
on a trunk.  Says I to myself: "I've got a loop between those
Upon investigation I find that *all three* of the links in
    the port 
channel are unidirectional.  There we go.  I move the
    channel to three 
different ports, different gbics, different fiber,
    blah blah...  happy 
network, happy users,

    The question:


    I may be as thick as Randy Bushs' wallet, and I've been away from the
catOS for some time, and I've never seen the like on a native, but I
don't quite get this.  It's highly improbable that all three of
interfaces (on three different line cards) went into this
    state.  Could 
one single interface in UD mode cause the entire
    channel to do that? 
Bear in mind that I didn't just assume each of
    these links was UD, I 
saw all three in that state from the cons.

    Anyone have a clue for me?

    ps: I know, I know, udld....  only been on the job two months and I
began my criticisms in the core.  :)

    p.p.s: by the way...  hi everybody.  :)
    HCE, Sep 11, 2006
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