Default Udld Configuration; Udld Aggressive And Nonaggressive Modes - Cisco AP775A - Nexus Converged Network Switch 5010 Configuration Manual

Information About Ethernet Interfaces
The following figure shows an example of a unidirectional link condition. Device B successfully receives
traffic from Device A on the port. However, Device A does not receive traffic from Device B on the same
port. UDLD detects the problem and disables the port.
Figure 7: Unidirectional Link

Default UDLD Configuration

The following table shows the default UDLD configuration.
Table 7: 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
Related Topics
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UDLD Aggressive and Nonaggressive Modes

UDLD aggressive mode is disabled by default. You can configure UDLD aggressive mode only on
point-to-point links between network devices that support UDLD aggressive mode. If UDLD aggressive mode
is enabled, when a port on a bidirectional link that has a UDLD neighbor relationship established stops
receiving UDLD frames, UDLD tries to reestablish the connection with the neighbor. After eight failed retries,
the port is disabled.
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 the UDLD aggressive mode, the following occurs:
• One side of a link has a port stuck (both transmission and receive)
OL-16597-01
Configuring the UDLD Mode, page 69
Default Value
Globally disabled
Disabled
Enabled on all Ethernet fiber-optic LAN ports
Disabled on all Ethernet 10/100 and 1000BASE-TX
LAN ports
Cisco Nexus 5000 Series Switch CLI Software Configuration Guide
Default UDLD Configuration
67