Port Management: Unidirectional Link Detection
Default Settings and Configuration
Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version) 151
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• UDLD and Layer 2 Protocols
UDLD runs on a port independently from other Layer 2 protocols running on
the same port, such as STP or LACP. For example, UDLD assigns the port a
status regardless of the STP status of the port or regardless of whether the
port belongs to a LAG or not.
Default Settings and Configuration
The following defaults exist for this feature:
• UDLD is disabled by default on all ports of the device.
• Default message time is 15 seconds.
• Default expiration time is 45 seconds (3 times the message time).
• Default port UDLD state:
- Fiber interfaces are in the global UDLD state.
- Non-fiber interfaces are in the disable state.
Before You Start
No preliminary tasks are required.
Common UDLD Tasks
This section describes some common tasks to setup UDLD.
Workflow1: To globally enable UDLD on fiber ports, perform the following
steps:
STEP 1 Open the Port Management > UDLD Global Settings page.
a. Enter the Message Time.
b. Select either Disabled, Normal or Aggressive as the global UDLD status.
