PAgP and STP

Hi folks,

Just read something in the LAN Switching book (page 273) and wanna double check if my understanding is correct.

If a group of links is configured using PAgP "ON" then only one link (which one?!!) will be used for STP and there is no fault tolerance in terms of STP messaging.

Does it mean the other mode (e.g. desirable) would lead to a STP-over-multi link situation?

 

Cheers,

K.

 

Comments

  • Hi,

    The link with the lowest port ID is used to send STP messages over a
    port-channel group. If that link leaves the group, the next link is used
    for STP messages. For example, if ports 0/13, 0/14, 0/15 are in channel
    (either static or negotiated) then port 0/13 is used for STP messages. The
    port ID in the STP message however is NOT port 13; AFAIR it starts with a
    high number (80 or something like this). Effectively, port-channel is
    interpreted as a single link from the STP standpoint.

    Petr Lapukhov

    ----- Original Message -----
    From: "Kami"
    Sent: Sat, June 20, 2009 19:38
    Subject:[CCIE R&S] PAgP and STP


    Hi folks,

    Just read something in the LAN Switching book (page 273) and wanna double
    check if
    my understanding is correct.

    If a group of links is configured using PAgP "ON" then
    only one link
    (which one?!!) will be used for STP and there is no fault tolerance in
    terms of STP
    messaging.

    Does it mean the other mode (e.g. desirable) would lead to a
    STP-over-multi link
    situation?



    Cheers,

    K.



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