Enabling Udld Aggressive Mode; Displaying The Udld Configuration - Cisco WS-X6066-SLB-APC - Content Switching Module Software Manual

Chapter 30 Configuring UDLD

Enabling UDLD Aggressive Mode

Software release 5.4(3) and later releases have 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 UDLD aggressive mode enabled, when a port on a
bidirectional link which has a UDLD neighbor relationship established stops receiving UDLD packets,
UDLD tries to reestablish the connection with the neighbor. After eight failed retries, the port is put into
errdisable state.
In order 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
(when default spanning tree parameters are used).
Enabling UDLD aggressive mode provides additional benefits in the following cases:
•
•
In these cases, UDLD aggressive mode errdisables one of the ports on the link and stops the blackholing
of traffic. Even with aggressive mode disabled, there would have been no risk for a broadcast storm due
to a spanning tree loop in this situation, as one port is unable to pass traffic in both directions.
Task
Step 1 Enable UDLD aggressive mode.
Step 2 Verify the configuration.
This example shows how to enable UDLD aggressive mode on the switch:
Console> (enable) set udld aggressive-mode enable 4/1
Aggressive UDLD enabled on port 4/1.
Console> (enable)
This example shows how to verify that UDLD aggressive mode is enabled on the switch:
Console> (enable) show udld port 4/1
UDLD
Message Interval: 30 seconds
Port
--------
4/1
Console> (enable)

Displaying the UDLD Configuration

To display the UDLD enable state, perform this task in privileged mode:
Task
Display the UDLD enable state.
78-13315-02
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
: enabled
Admin Status Aggressive Mode Link State
------------ --------------- ---------
enabled Enabled
Command
set udld aggressive-mode enable mod/port
show udld
bidirectional
Command
show udld
Catalyst 6000 Family Software Configuration Guide—Releases 6.3 and 6.4
Configuring UDLD
30-5