28-5
Software Configuration Guide—Release 15.0(2)SG
OL-23818-01
Chapter 28 Configuring UDLD
Configuring UDLD on the Switch
Enabling UDLD Globally
To enable UDLD in aggressive or normal mode and to set the configurable message timer on all
fiber-optic interfaces on the switch, perform this task:
Command Purpose
Step 1
Switch# configure terminal
Enters the global configuration mode.
Step 2
Switch(config)# udld {aggressive | enable |
message time message-timer-interval} | fast-hello
error-reporting
Specifies UDLD and Fast UDLD operation:
• aggressive —Enables UDLD in aggressive mode on
all fiber-optic interfaces.
• enable —Enables UDLD in normal mode on all
fiber-optic interfaces on the switch. UDLD is
disabled by default.
An individual interface configuration overrides the
setting of the udld enable global configuration
command.
For more information about aggressive and normal
modes, see the “Operation Modes” section on
page 28-3.
• message time —message-timer-interval—
Configures the period of time between UDLD probe
messages on ports that are in the advertisement
phase and are determined to be bidirectional. The
range is from 1 to 90 seconds.
Note Prior to Cisco IOS Release 12.2(31)SGA, the
timer range is 7 to 90 seconds. With
Cisco IOS Release 12.2(31)SGA, the timer range
is 1 to 90 seconds.
• fast-hello error reporting—If configured, Fast
UDLD does not errdisable a unidirectional link.
Instead, a log message informing link failure is
displayed on the console (behavior for fast UDLD
only).
Step 3
Switch(config)# end
Returns to privileged EXEC mode.
Step 4
Switch# show udld
Verifies the configuration.
