one-way link of copper UTP

Unanswered Question
Dec 27th, 2007
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4506 ws-4448G-T<--->glc-t 3560,


1. on 4506, show cdp nei ,can find 3560,

but 3560 can't find 4506.


2. no bpdu exchange, both 3560 and 4506 are root bridge.


3.IP can be transfered without any problem.


I try 1000G crossover UTP instead of straight-through UTP, but same problem...

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umedryk Thu, 01/03/2008 - 11:21
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A unidirectional link occurs whenever the traffic that is transmitted by the local device over a link is received by the neighbor but the traffic that is transmitted from the neighbor is not received by the local device. If one of the fiber strands in a pair is disconnected, as long as autonegotiation is active, the link does not stay up. In this case, the logical link is undetermined, and UDLD does not take any action. If both fibers are working normally from a Layer 1 perspective, then UDLD at Layer 2 determines whether those fibers are connected correctly and whether the traffic is flowing bidirectionally between the right neighbors. This check cannot be performed by autonegotiation, because autonegotiation is a Layer 1 mechanism.

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/catos/8.x/configuration/guide/udld.html

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