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UDLD Software and Hardware Requirements
The switch periodically transmits UDLD messages (packets) to neighbor devices on ports with UDLD
enabled. If the messages are echoed back to the sender within a specific time frame and they are lacking
a specific acknowledgment (echo), the link is flagged as unidirectional and the port 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.
With software release 5.4(3) and later releases, you can specify the message interval between UDLD
Note
messages. Previously, the message interval was fixed at 60 seconds. With a configurable message interval,
UDLD reacts much faster to link failures.
Figure 23-1
from Switch A on the port. However, Switch A does not receive traffic from Switch B on the same port.
UDLD detects the problem and disables the port.
Figure 23-1 Unidirectional Link
TX
TX
UDLD Software and Hardware Requirements
UDLD requires the following hardware and software:
•
•
Default UDLD Configuration
Table 23-1
Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide
23-2
shows an example of a unidirectional link condition. Switch B successfully receives traffic
Switch A
RX
RX
Switch B
For fiber-optic links:
Software release 5.1 or later releases
–
–
Ethernet, Fast Ethernet, or Gigabit Ethernet fiber-optic switching modules
For copper links:
–
Software release 5.2 or later releases
Ethernet or Fast Ethernet copper switching modules
–
shows the default UDLD configuration.
Chapter 23
Configuring UDLD
—
Release 8.1
78-15486-01
- Quick Links:
- Configuration Guide
- Catalyst 2980G Switch
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