Cisco Systems SG50028PK9NA Manual De Usuario

Usage Guidelines

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Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version) 

UDLD again begins running on the port. If the link is still unidirectional, UDLD 
shuts it down again after the UDLD expiration time expires, for instance.

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Manually—You can reactivate a port in the Port Management > Error 
Recovery Settings page

Cisco does not recommend enabling UDLD on ports that are connected to 
devices on which UDLD is not supported or disabled. Sending UDLD packets on a 
port connected to a device that does not support UDLD simply causes more 
traffic on the port without providing benefits.

In addition, take the following into consideration when configuring UDLD:

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Set the message time according to how urgent it is to shut down ports with 
a unidirectional link. The lower the message time, the more UDLD packets 
are sent and analyzed, but the sooner the port is shut down if the link is 
unidirectional.

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If you want UDLD to be enabled on a copper port, you must enable it per 
port. When you globally enable UDLD, it is only enabled on fiber ports.

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Set the UDLD mode to normal when you do not want to shut down ports 
unless it is known for sure that the link is unidirectional. 

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Set the UDLD mode to aggressive when you want to shut down any port 
whenever there is even a chance that the link is undetermined.

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UDLD and Layer 1. 

When UDLD is enabled on a port, UDLD actively runs on that port while the 
port is up. When the port is down, UDLD goes into UDLD shutdown state. In 
this state, UDLD removes all learned neighbors. When the port is changed 
from down to up, UDLD resumes actively running.