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Cisco Nexus 5500 Series NX-OS Layer 2 Interfaces Command Reference
OL-27880-02
Chapter U Commands
udld (configuration mode)
udld (configuration mode)
To configure the Unidirectional Link Detection (UDLD) protocol on the switch, use the
udld
command.
To disable UDLD, use the
no
form of this command.
udld
{
aggressive
|
message-time
timer-time
|
reset
}
no udld
{
aggressive
|
message-time
|
reset
}
Syntax Description
Command Default
Disabled
Command Modes
Global configuration mode
Command History
Usage Guidelines
UDLD aggressive mode is disabled by default. You can configure UDLD aggressive mode only on
point-to-point links between network devices that support UDLD aggressive mode. If UDLD aggressive
mode is enabled, when a port on a bidirectional link that has a UDLD neighbor relationship established
stops receiving UDLD frames, UDLD tries to reestablish the connection with the neighbor. After eight
failed retries, the port is disabled.
To prevent spanning tree loops, normal UDLD with the default interval of 15 seconds is fast enough to
shut down a unidirectional link before a blocking port transitions to the forwarding state (with default
spanning tree parameters).
When you enable the UDLD aggressive mode, the following occurs:
•
One side of a link has a port stuck (both transmission and receive)
•
One side of a link remains up while the other side of the link is down
In these cases, the UDLD aggressive mode disables one of the ports on the link, which prevents traffic
from being discarded.
Examples
This example shows how to enable the aggressive UDLD mode for the switch:
switch#
configure terminal
aggressive
Enables UDLD in aggressive mode on the switch.
message-time
timer-time
Sets the period of time between UDLD probe messages on ports that are in
advertisement mode and are currently determined to be bidirectional. The
range is from 7 to 90 seconds. The default is 15 seconds.
reset
Resets all the ports that are shut down by UDLD and permit traffic to begin
passing through them again. Other features, such as spanning tree, will
behave normally if enabled.
Release
Modification
5.2(1)N1(1)
This command we introduced.
