Edge-Core ECS4660-28F, Management Manual, Page: 1266 / 2020

C
HAPTER
36
| UniDirectional Link Detection Commands
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If the link is deemed anything other than bidirectional at the end of the
detection phase, this curve becomes a flat line with a fixed value of Mfast
(7 seconds).
If the link is instead deemed bidirectional, the curve will use Mfast for the
first four subsequent message transmissions and then transition to an
Mslow value for all other steady-state transmissions. Mslow is the value
configured by this command.
E
XAMPLE
This example sets the message interval to 10 seconds.
Console(config)#udld message-interval 10
Console(config)#
udld aggressive
This command sets UDLD to aggressive mode on an interface. Use the no
form to restore the default setting.
S
YNTAX
[ no ] udld aggressive
D
EFAULT
S
ETTING
Disabled
C
OMMAND
M
ODE
Interface Configuration (Ethernet Port)
C
OMMAND
U
SAGE
UDLD can function in two modes: normal mode and aggressive mode.
◆
In normal mode, determination of link status at the end of the
detection process is always based on information received in UDLD
messages: whether that’s information about the exchange of proper
neighbor identification or the absence of such. Hence, albeit bound by a
timer, normal mode determinations are always based on gleaned
information, and as such are “event-based.” If no such information can
be obtained (e.g., because of a bidirectional loss of connectivity), UDLD
follows a conservative approach minimize false positives during the
detection process and deems a port to be in “undetermined” state. In
other words, normal mode will shut down a port only if it can explicitly
determine that the associated link is faulty for an extended period of
time.
◆
In aggressive mode, UDLD will also shut down a port if it loses
bidirectional connectivity with the neighbor for the same extended
period of time (as that mentioned above for normal mode) and
subsequently fails repeated last-resort attempts to re-establish
communication with the other end of the link. This mode of operation
assumes that loss of communication with the neighbor is a meaningful
network event in itself, and a symptom of a serious connectivity