Web Management Guide

Table Of Contents
Chapter 12
| Basic Administration Protocols
UDLD Configuration
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UDLD Configuration
The switch can be configured to detect general loopback conditions caused by
hardware problems or faulty protocol settings. When enabled, a control frame is
transmitted on the participating ports, and the switch monitors inbound traffic to
see if the frame is looped back.
Usage Guidelines
The default settings for the control frame transmit interval and recover time
may be adjusted to improve performance for your specific environment. The
shutdown mode may also need to be changed once you determine what kind
of packets are being looped back.
General loopback detection provided by the commands described in this
section and loopback detection provided by the spanning tree protocol cannot
both be enabled at the same time. If loopback detection is enabled for the
spanning tree protocol, general loopback detection cannot be enabled on the
same interface.
When a loopback event is detected on an interface or when a interface is
released from a shutdown state caused by a loopback event, a trap message is
sent and the event recorded in the system log.
Loopback detection must be enabled both globally and on an interface for
loopback detection to take effect.
Configuring UDLD
Protocol Intervals
Use the Administration > UDLD > Configure Global page to configure the
UniDirectional Link Detection message probe interval, detection interval, and
recovery interval.
Parameters
These parameters are displayed:
Message Interval
– Configures the message interval between UDLD probe
messages for ports in the advertisement phase and determined to be
bidirectional. (Range: 7-90 seconds; Default: 15 seconds)
UDLD probe messages are sent after linkup or detection phases. During the
detection phase, messages are exchanged at the maximum rate of one per
second. After that, if the protocol reaches a stable state and determines that the
link is bidirectional, the message interval is increased to a configurable value
based on a curve known as M1(t), a time-based function described in RFC 5171.
If the link is deemed anything other than bidirectional at the end of the
detection phase, this curve becomes a flat line with a fixed value of Mfast (7
seconds).
If the link is instead deemed bidirectional, the curve will use Mfast for the first
four subsequent message transmissions and then transition to an Mslow value