Testing UDLD on copper interfaces

Discussion in 'Cisco' started by ango, Oct 27, 2009.

  1. ango

    ango Guest

    Hi all,

    I have to verify the correct working of UDLD protocol on copper
    interfaces.
    In my lab two 6509 Catalysts are connected betweeen them with
    4x10/100/1000 links, taken form a WS-X6148A-GE-TX port adapter. An
    Etherchannel is used to combine these links into one logical channel.
    Autonegotiation is already enabled on the involved interfaces and
    Rapid Spanning Tree is configured.

    I'm planning to enable aggressive UDLD on all these interfaces with
    the "udld port aggressive" command; I'm looking a way to test if it
    works. I think the most critical point would be how to simulate an
    unidirectional link.

    Any idea how to implement it? I''ve read on a forum about one possible
    strategy: to put a non-Cisco L2 device between the two Catalysts and
    unplug one side after the UDLD peers have been created.

    Has anyone tested it successfully? Any other suggestion about
    alternative ways to have an unidirectional link on copper interfaces?

    Thanks
    Alessandro
     
    ango, Oct 27, 2009
    #1
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  2. ango

    Stephen Guest

    On Tue, 27 Oct 2009 07:40:21 -0700 (PDT), ango
    <> wrote:

    >Hi all,
    >
    >I have to verify the correct working of UDLD protocol on copper
    >interfaces.
    >In my lab two 6509 Catalysts are connected betweeen them with
    >4x10/100/1000 links, taken form a WS-X6148A-GE-TX port adapter. An
    >Etherchannel is used to combine these links into one logical channel.
    >Autonegotiation is already enabled on the involved interfaces and
    >Rapid Spanning Tree is configured.


    please note these blades are contended and not designed for trunk
    pipes.

    a set of 6 or 8 ports shares 1 chip, and a single GigE internal
    connection.

    if you must build an Etherchannel, make sure you combine ports from
    different "sets" or you are going to be limited to 1 Gbps anyway.
    >
    >I'm planning to enable aggressive UDLD on all these interfaces with
    >the "udld port aggressive" command; I'm looking a way to test if it
    >works. I think the most critical point would be how to simulate an
    >unidirectional link.
    >
    >Any idea how to implement it? I''ve read on a forum about one possible
    >strategy: to put a non-Cisco L2 device between the two Catalysts and
    >unplug one side after the UDLD peers have been created.
    >
    >Has anyone tested it successfully? Any other suggestion about
    >alternative ways to have an unidirectional link on copper interfaces?
    >
    >Thanks
    >Alessandro

    --
    Regards

    - replace xyz with ntl
     
    Stephen, Oct 27, 2009
    #2
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  3. ango

    bod43 Guest

    On 28 Oct, 00:44, "Tosh" <> wrote:
    > > Any idea how to implement it? I''ve read on a forum about one possible
    > > strategy: to put a non-Cisco L2 device between the two Catalysts and
    > > unplug one side after the UDLD peers have been created.

    >
    > Maybe I miss something but it doesn't seem to me an effective way to test
    > udld, as far as I know the most flexible way is to build a link with a
    > couple of fiber media converters and plug/unplug each simplex fiber
    > connector in order to close/open the link in any direction you like.
    > Bye,
    >         Tosh.


    Maybe you can block the UDLD packets with a mac access-list?
    UDLD uses the same destination mac as CDP.

    If that does not work maybe a non-cisco intermediate switch
    that supported mac ACLs might work.

    Remember too that GBE already protects against
    unidirectional links. I am not sure of the details but my
    understanding is that there is a physical layer
    protocol within GBE that ensures that neither
    port will up come unless both come up. Maybe
    worth reading the GBE standard which may be free
    from the IEEE.
     
    bod43, Oct 28, 2009
    #3
  4. ango

    Stephen Guest

    On Wed, 28 Oct 2009 03:31:18 -0700 (PDT), bod43 <>
    wrote:

    >On 28 Oct, 00:44, "Tosh" <> wrote:
    >> > Any idea how to implement it? I''ve read on a forum about one possible
    >> > strategy: to put a non-Cisco L2 device between the two Catalysts and
    >> > unplug one side after the UDLD peers have been created.

    >>
    >> Maybe I miss something but it doesn't seem to me an effective way to test
    >> udld, as far as I know the most flexible way is to build a link with a
    >> couple of fiber media converters and plug/unplug each simplex fiber
    >> connector in order to close/open the link in any direction you like.
    >> Bye,
    >>         Tosh.

    >
    >Maybe you can block the UDLD packets with a mac access-list?
    >UDLD uses the same destination mac as CDP.
    >
    >If that does not work maybe a non-cisco intermediate switch
    >that supported mac ACLs might work.
    >
    >Remember too that GBE already protects against
    >unidirectional links. I am not sure of the details but my
    >understanding is that there is a physical layer
    >protocol within GBE that ensures that neither
    >port will up come unless both come up. Maybe
    >worth reading the GBE standard which may be free
    >from the IEEE.


    GigE includes negotiation which should sort out a local 1 way link
    issue. If you have just fibre between the 2 ciscos then that should be
    it.

    It doesnt tend to work if there are intermediate devices mucking
    around with the bit stream since the negoiation is interface to
    adjacent interface.

    I stumbled over this with a GigE over SDH module in a Marconi /
    Ericsson mux.

    FWIW 802.1q link aggregation should also detect "break" style faults
    since the protocol involves exchanging hello packets on each link.

    You may want to see what you get with a marginal fault where some
    proportion of the traffic gets trashed - these kinds of issue seem
    harder to find and troubleshoot, esp where you use load balancing
    across Ethernet links.
    --
    Regards

    - replace xyz with ntl
     
    Stephen, Oct 29, 2009
    #4
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