Configuring Unidirectional Link Detection; Creating Etherchannel Port Groups - Cisco WS-C2955T-12 Software Manual

Chapter 7 Configuring the Switch Ports

Configuring UniDirectional Link Detection

UniDirectional Link Detection (UDLD) is a Layer 2 protocol that detects and shuts down unidirectional links.
You can configure UDLD on the entire switch or on an individual port. Use the udld reset command to
reset all ports that have been shut down by UDLD.
Beginning in privileged EXEC mode, follow these steps to configure UDLD on a switch:
Command
Step 1
configure terminal
Step 2 udld enable
Step 3
end
Step 4
show running-config
Use the errdisable detect cause udld global configuration command to automatically place a port in
error-disabled state, which is an operational state similar to link-down state, when a UDLD-related error
condition is detected on the port.
The errdisable recovery global configuration command automatically re-enables the port after a
specified time, so that the port can try the operation again. The port would continue the error disable and
recovery cycle until the UDLD error condition no longer exists.
The errdisable commands are not available on the Catalyst 2900 LRE XL switches.
Note

Creating EtherChannel Port Groups

Fast EtherChannel (FEC) and Gigabit EtherChannel port groups act as single, logical ports for
high-bandwidth connections between switches or between switches and servers.
You can create port groups of either Gigabit Ethernet ports or 100BASE-TX ports, but you cannot create
Note
a port group that has both port speeds.
For the restrictions that apply to port groups, see the
page
78-6511-08
Purpose
Enter global configuration mode.
Enable UDLD on all switch ports.
Use the udld interface configuration command to enable UDLD on a
specific port.
Return to privileged EXEC mode.
Verify the entry by displaying the running configuration.
9-7.
Catalyst 2900 Series XL and Catalyst 3500 Series XL Software Configuration Guide
Configuring UniDirectional Link Detection
"Avoiding Configuration Conflicts" section on
7-7