sh glbp [brief]

Discussion in 'Cisco' started by alex, Aug 8, 2012.

  1. alex

    alex Guest

    Hi there,

    is there anyone who can explain the output of the command in the subject?
    I don't know why it looks not consistent across the memebers
    partecipating in the GLBP group.

    Especially the state column: listen, active and STANDBY.

    I understand somehow that active refers to the IP address that is active
    in the router where the command is performed and listen means that such
    router is listening to that neighbour but I cannot understand why on the
    standby router I do have the label standby for what is actually the AVG,

    Also I don't know why in a router that is not neither the AVG nor the
    standby VG I canno differentiate who's the active and who's the standby
    VG.

    If you have dealt with GLBP or if you would share your ideas on it with
    me it will be appreciated a lot.

    Thanks!

    Alex
     
    alex, Aug 8, 2012
    #1
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  2. Hi Alex
    I used to have to worry about this. Perhaps you can post the output you are
    looking at so we all can see.

    Rgds,
    Martin
     
    Martin Gallagher, Aug 9, 2012
    #2
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  3. alex

    alex Guest

    Unfortunately my dynamips crashed but I can refer to this link

    http://cciethebeginning.wordpress.com/2008/09/06/glbp-gateway-load-balancing-protocol/

    from where I picked the following (sorry is not formatted with courier
    character):

    R2#sh glbp brief
    Interface Grp Fwd Pri State Address Active router Standby route
    Fa1/0 10 – 100 Standby 10.20.20.1 10.20.20.3 local
    Fa1/0 10 1 7 Listen 0007.b400.0a01 10.20.20.3 -
    Fa1/0 10 2 7 Active 0007.b400.0a02 local -
    Fa1/0 10 3 7 Listen 0007.b400.0a03 10.20.20.4 -

    Anyway I gave myself an explanation and the conclusion I came to is that
    the first line is completely not linked to the remaining ones, meaning
    the way you read it is different from how you read the rest of the
    output.

    This way from the 2nd onwards the output is more coherent.

    I don't know if you had the same difficulty in reading this output but
    please share your thoughts.

    Thanks,

    Alex
     
    alex, Aug 9, 2012
    #3
  4. Hello Alex,
    Yes. There are two diffrent roles in GLBP, Virtual Gateway (VG) and Virtual
    Forwarder (VF).

    VG is like in HSRP and the first line descibes the VG information:

    This router is the Standby router.
    The Virtual IP addres is 10.20.20.1
    The Active router is 10.20.20.3

    In HSRP only one router forwards traffic. In GLBP you can have up 4
    forwarders and lines 2-4 in the output describe the Virtual forwarders:

    There are three forwarders.
    10.20.20.3 using MAC address 0007.b400.0a01
    10.20.20.4 using MAC address 0007.b400.0a03
    This router using MAC address 0007.b400.0a02

    REF:
    ====
    GLBP - Gateway Load Balancing Protocol
    http://www.cisco.com/en/US/docs/ios/12_2t/12_2t15/feature/guide/ft_glbp.html
     
    Martin Gallagher, Aug 10, 2012
    #4
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