Specifying The Udld Message Interval; Enabling Udld Aggressive Mode - Cisco WS-C2948G-GE-TX Configuration Manual

Chapter 23 Configuring UDLD

Specifying the UDLD Message Interval

To specify the UDLD message interval, perform this task in privileged mode:
Task
Step 1
Specify the UDLD message interval.
Step 2
Verify the configuration.
This example shows how to specify the UDLD message interval:
Console> (enable) set udld interval 10
UDLD message interval set to 10 seconds
Console> (enable)
This example shows how to verify the message interval:
Console> (enable) show udld
UDLD
Message Interval
Console> (enable)

Enabling UDLD Aggressive Mode

Software release 5.4(3) and later releases support UDLD aggressive mode. UDLD aggressive mode is
disabled by default and its use is recommended only for point-to-point links between Cisco switches
running software release 5.4(3) or later releases. With aggressive mode enabled, when a port on a
bidirectional link stops receiving UDLD packets, UDLD tries to reestablish the connection with the
neighbor. After eight failed retries, the port is put into errdisable state.
To prevent spanning tree loops, normal UDLD with a 15-second message interval is fast enough to shut
down a unidirectional link before a blocking port transitions to forwarding state (when default spanning
tree parameters are used).
Enabling UDLD aggressive mode provides additional benefits in the following cases:
•
•
In these cases, UDLD aggressive mode error disables one of the ports on the link and stops the loss of
traffic. Even with aggressive mode disabled, there is no risk for a broadcast storm due to a spanning tree
loop in this situation, because one port cannot pass traffic in both directions.
To enable UDLD aggressive mode on module ports, perform this task in privileged mode:
Task
Step 1 Enable UDLD aggressive mode.
Step 2
Verify the configuration.
This example shows how to enable UDLD aggressive mode:
Console> (enable) set udld aggressive-mode enable 4/1
Aggressive UDLD enabled on port 4/1.
Console> (enable)
Catalyst 4500 Series, Catalyst 2948G, Catalyst 2948G-GE-TX, and Catalyst 2980G Switches Software Configuration Guide—Release 8.2GLX
78-15908-01
: enabled
: 10 seconds
One side of a link has a port stuck (both Tx and Rx)
One side of a link remains up while the other side of the link has gone down
Command
set udld interval interval
show udld
Command
set udld aggressive-mode enable mod_num/port_num
show udld
Configuring UDLD on the Switch
23-5