Charlie Wehner wrote:
Will UDLD prevent duplex mismatches from occurring on end user
devices? (Disabling a ports that are detected to be mismatched)
Cisco's Unidirectional Link Detection protocol requires the two ends of the
link to send UDLD messages to each other. An end-user device wouldn't
understand the protocol and wouldn't send the messages.
Or does UDLD only work between switches?
It only works between switches, unless NIC vendors have implemented it, but
I haven't heard that any have.
UDLD probably won't help detect a duplex mismatch anyway. A link that has a
duplex mismatch problem isn't unidirectional. It's bidirectional but
hampered by errors and collisions, depending on traffic flow, rates, and load.
For UDLD to help with a duplex mismatch problem, the message interval would
have to be extremely small. The default for the interval is 15 seconds.
Unfortunately, the lowest you can set it is 7 seconds. With UDLD aggressive
mode, if one side detects a problem it does start sending UDLD packets every
second, which could help, but probably wouldn't help on most links.
When there's a duplex mismatch, the side using half duplex will have
problems sending, but the problem probably won't last for an entire second.
Ethernet retransmissions occur in milliseconds, not seconds.
UDLD helps with wiring faults, such as the receive and transmit fibers not
being connected to the same port on the remote side, and
misbehaving ports that can send but not receive or vice versa, but it's not
much help with a duplex mismatch problem on a link with typical traffic
characteristics.
Priscilla
Thanks in Advance
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7i=66463t=66461
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