udld doubt

Discussion in 'Cisco' started by cheeku, May 31, 2007.

  1. cheeku

    cheeku Guest

    Cisco's documentation says
    "If both fibers are working normally at Layer 1, then UDLD at Layer 2
    determines whether those fibers are connected correctly and whether
    traffic is flowing bidirectionally between the correct neighbors. This
    check cannot be performed by autonegotiation, because autonegotiation
    is a Layer 1 feature."

    layer 1 determines if there exists a proper physical connection
    between the 2 communicating devices........right?
    if there is some problem with either the TX. or RX. fibers,then that
    will be detected at the physical layer itself......right?
    then what does udld do?
    Cisco's documentation says
    "Layer 2 determines whether those fibers are connected correctly and
    whether traffic is flowing bidirectionally between the 'correct'
    neighbors. "
    what do you mean by correct neighbors
     
    cheeku, May 31, 2007
    #1
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  2. cheeku

    CescoAiel Guest

    On May 31, 4:12 am, cheeku <> wrote:
    > Cisco's documentation says
    > "If both fibers are working normally at Layer 1, then UDLD at Layer 2
    > determines whether those fibers are connected correctly and whether
    > traffic is flowing bidirectionally between the correct neighbors. This
    > check cannot be performed by autonegotiation, because autonegotiation
    > is a Layer 1 feature."
    >
    > layer 1 determines if there exists a proper physical connection
    > between the 2 communicating devices........right?
    > if there is some problem with either the TX. or RX. fibers,then that
    > will be detected at the physical layer itself......right?
    > then what does udld do?
    > Cisco's documentation says
    > "Layer 2 determines whether those fibers are connected correctly and
    > whether traffic is flowing bidirectionally between the 'correct'
    > neighbors. "
    > what do you mean by correct neighbors


    tx1->rx2
    tx2->rx3
    tx3->rx1

    Fibres will be lit, layer 1 assumes to be up, but no traffic can flow,
    because fibres got mixed up... UDLD will detect this for you!
     
    CescoAiel, Jun 6, 2007
    #2
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