Cisco 350XG series Administration Manual page 187

Port Management
UDLD
Cisco 350XG & 550XG Series 10G Stackable Managed Switches
UDLD Not Supported or is Disabled on a Neighbor
If UDLD is not supported or disabled on a neighbor, then no UDLD messages are
received from that neighbor. In this case, the device cannot determine whether the
link is unidirectional or bidirectional. The status of the interface is then set to
undetermined.
Reactivating a Shutdown Port
You can reactivate a port that was shut down by UDLD in one of the following
ways:
• Automatically—You can configure the system to automatically reactivate
ports shut down by UDLD in the
case, when a port is shut down by UDLD, it is automatically reactivated
when the automatic recovery interval expires. 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.
• Manually—You can reactivate a port in the
Usage Guidelines
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 causes more traffic on the
port without providing benefits.
In addition, take the following into consideration when configuring UDLD:
• 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.
• 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.
• 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.
• Set the UDLD mode to aggressive when you want both unidirectional and
bidirectional link loss.
Error Recovery Settings
Error Recovery Settings
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