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Forum Replies

  1. Hello Renne,

    Does UDLD will work from cisco 4500 to a 3rd party switch (IBM g8264)

    -I configured the cisco 4500 on a normal mode and on the other side, the port is also on the normal mode
    -tried to filter the mac address for udld but the port is still operational.

    Do you think that when udld is deployed on cisco with a non cisco equipment, will they still use the udld mac address you mentioned or it is cisco proprietary?

    Thank you.

  2. Hi Thomas,

    1. Nope, once something happens on either side…the link will go down. There’s no separate transmit or receive connect with copper links. One topic that is related that you might like is BFD:

    https://networklessons.com/cisco/ccie-routing-switching/bidirectional-forwarding-detection-bfd/

    1. You should use it on the blocking (alternate) ports but also on root ports, basically any port that could be in blocking mode if the topology changes. You can enable it globally like I did.

    2. Loopguard works based on BPDUs (L2 information). If a loopguard enabled no

    ... Continue reading in our forum

  3. Alan,
    You are correct. Cisco recommends that loopguard not be enabled on Designated Ports. Root Bridges, by definition, have nothing but DPs. Therefore, loopguard should not be enabled on it.

    Specifically, Cisco says:
    Loop guard must be enabled on the non-designated ports (more precisely, on root and alternate ports) for all possible combinations of active topologies

    Source:
    http://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/10596-84.html#loop_guard_considerations

  4. Wisam

    My sincere apologies, I forgot to add the link. You can find the document here.

    Laz

  5. Hi Ray,

    This is no problem. Without loop guard, if a non-designated port stops receiving BPDUs then it goes through the listening > learning > forwarding state.

    When you enable loop guard then a non-designated port that receives no BPDUs goes into a inconsistent state instead of going through the listening > learning > forwarding state. It does not affect designated ports.

    Rene

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