Default Udld Configuration; Enabling Udld Globally - Cisco 7604 Configuration Manual

Chapter 49 Configuring UDLD
To prevent spanning tree loops, nonaggressive 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 UDLD aggressive mode, you receive additional benefits in the following situations:
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In these cases, UDLD aggressive mode disables one of the ports on the link, which prevents traffic from
being discarding.
In UDLD normal mode, when a unidirectional error is detected, the port is not disabled. In UDLD
Note
aggressive mode, when a unidirectional error is detected, the port is disabled.

Default UDLD Configuration

Table 49-1
Table 49-1 UDLD Default Configuration
Feature
UDLD global enable state
UDLD aggressive mode
UDLD per-port enable state for fiber-optic media
UDLD per-port enable state for twisted-pair (copper) media
Configuring UDLD
These sections describe how to configure UDLD:
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Enabling UDLD Globally

To enable UDLD globally on all fiber-optic LAN ports, perform this task:
OL-4266-08
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
shows the default UDLD configuration.
Enabling UDLD Globally, page 49-3
Enabling UDLD on Individual LAN Interfaces, page 49-4
Disabling UDLD on Fiber-Optic LAN Interfaces, page 49-4
Configuring the UDLD Probe Message Interval, page 49-5
Displaying Disabled LAN Interfaces, page 49-5
Displaying UDLD Neighbor Interfaces, page 49-5
Resetting Disabled LAN Interfaces, page 49-5
Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
Default Value
Globally disabled
Disabled
Enabled on all Ethernet fiber-optic LAN ports
Disabled on all Ethernet 10/100 and 1000BASE-TX LAN
ports
Default UDLD Configuration
49-3