Cisco Systems WSC4500X16SFP Manual De Usuario
20-2
Software Configuration Guide—Release 12.2(25)SG
OL-7659-03
Chapter 20 Configuring UDLD
Default UDLD Configuration
The switch periodically transmits UDLD packets to neighbor devices on interfaces with UDLD enabled.
If the packets are echoed back within a specific time frame and they are lacking a specific
acknowledgment (echo), the link is flagged as unidirectional and the interface is shut down. Devices on
both ends of the link must support UDLD in order for the protocol to successfully identify and disable
unidirectional links.
If the packets are echoed back within a specific time frame and they are lacking a specific
acknowledgment (echo), the link is flagged as unidirectional and the interface is shut down. Devices on
both ends of the link must support UDLD in order for the protocol to successfully identify and disable
unidirectional links.
Note
By default, UDLD is locally disabled on copper interfaces to avoid sending unnecessary control traffic
on this type of media, since it is often used for access interfaces.
on this type of media, since it is often used for access interfaces.
shows an example of a unidirectional link condition. Switch B successfully receives traffic
from Switch A on the interface. However, Switch A does not receive traffic from Switch B on the same
interface. UDLD detects the problem and disables the interface.
interface. UDLD detects the problem and disables the interface.
Figure 20-1 Unidirectional Link
Default UDLD Configuration
shows the UDLD default configuration.
Configuring UDLD on the Switch
The following sections describe how to configure UDLD:
•
•
•
•
•
TX
TX
RX
RX
Switch A
Switch B
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Table 20-1 UDLD Default Configuration
Feature
Default Status
UDLD global enable state
Globally disabled
UDLD per-interface enable state for fiber-optic media
Enabled on all Ethernet fiber-optic interfaces
UDLD per-interface enable state for twisted-pair (copper) media Disabled on all Ethernet 10/100 and 1000BaseTX
interfaces