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VCP protcol PDU in Virtual chassis and metric value

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  • 1.  VCP protcol PDU in Virtual chassis and metric value

    Posted 12-15-2018 16:34

    Hi everyone,

    1)Virtual chassis protocol factors two things in computing the shortest path from rooted PFE to target PFE.

    a) bandwidth 

    b) hop count.



    From the above link:

    When all interfaces have the same bandwidth, as is the case here, the SPF result is effectively based on hop count.


    This is what I understand:

    SPF first factors in bandwidth in computing the shortest path, if tie, it then considers the hop count to compute the shoretst path from " rooted " PFE to target PFE.

    Is my understanding correct?


    2)  VCCP uses ISIS protcol .

    Cisco implementation uses default metric of 10 for all ISIS enabled links. It does not matter if the link is 10 G or 1 G, this metric is then used to compute the shortest path.

    In JUNOS' implementation  , do we have default value too,  regardless of the link bandwidth just like we see in Cisco?


    Below I  see metric value of 15 , I am not sure if this the deafult value or if this value was computed using bandwidth as we see in  OSPF?



    From the above link:

    user@host> show virtual-chassis protocol database member 0 detail

    001d.b510.0800.00-00 Sequence: 0x9f5, Checksum: 0x5b2b, Lifetime: 116 secs
       Neighbor: b0c6.9abf.6800.00  Interface: vcp-1/3/0.32768 Metric:      15
    b0c6.9abf.6800.00-00 Sequence: 0x9f8, Checksum: 0x326e, Lifetime: 117 secs
       Neighbor: 001d.b510.0800.00  Interface: vcp-5/0/0.32768 Metric:      15


    Thanks and have a nice weekend!!










  • 2.  RE: VCP protcol PDU in Virtual chassis and metric value
    Best Answer

    Posted 12-16-2018 04:58

    I can't find documentation that details this, but it seems to be based on the port bandwidth.  On VC using the build in port I see a metric of 7.