Simple stupid fiber question on Cisco 7301 and 3550 switch

Discussion in 'Cisco' started by Rea Michaels, Jul 19, 2004.

  1. Rea Michaels

    Rea Michaels Guest

    A customer I spoke with has a Cisco 7301 router with
    GigabitEthernet0/1 plugged in to a 3550 switch. The customer claims
    the GigabitEthernet0/1 on the Cisco 7301 showed down, but the 3550
    switch showed the circuit up. I'm a fiber newbie, so my simple stupid
    question is; Can one side of a fiber ciruit show up, and the other
    side show down?"

    Thanks,

    Rea
    Rea Michaels, Jul 19, 2004
    #1
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  2. In article <40fc220a.2211770@127.0.0.1>,
    Rea Michaels <> wrote:
    : A customer I spoke with has a Cisco 7301 router with
    :GigabitEthernet0/1 plugged in to a 3550 switch. The customer claims
    :the GigabitEthernet0/1 on the Cisco 7301 showed down, but the 3550
    :switch showed the circuit up. I'm a fiber newbie, so my simple stupid
    :question is; Can one side of a fiber ciruit show up, and the other
    :side show down?"

    It happens. I've never seen an explanation for it, but I have seen
    people posting here saying it has happened to them.


    Some possibilities pulled out of thin air:

    - sensitivities of the receivers differ, the link is borderline,
    the connectors need to be cleaned

    - gigabit is spec'd to automatically figure out details like crossovers
    and duplex, but there have been reports that it doesn't always work on
    all manufacturers

    - difference between "line protocol is up" and "line is administratively
    up"
    --
    How does Usenet function without a fixed point?
    Walter Roberson, Jul 19, 2004
    #2
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  3. Rea Michaels

    fearo Guest

    On Mon, 19 Jul 2004 19:34:15 +0000, Rea Michaels wrote:

    >
    > A customer I spoke with has a Cisco 7301 router with
    > GigabitEthernet0/1 plugged in to a 3550 switch. The customer claims the
    > GigabitEthernet0/1 on the Cisco 7301 showed down, but the 3550 switch
    > showed the circuit up. I'm a fiber newbie, so my simple stupid question
    > is; Can one side of a fiber ciruit show up, and the other side show down?"
    >
    > Thanks,
    >
    > Rea


    There are two things that come to mind in this situation that I have seen
    myself.

    1) port negotiation. Best results are achieved with this disabled on both
    ends.

    2) flow control. Best results if both ends are set to "desired" for send
    and recieve packets.
    fearo, Jul 21, 2004
    #3
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