Cisco 7206 - VXR Router Configuration Manual page 33

Chapter 2 Configuring Basic Interface Parameters
S e n d d o c u m e n t c o m m e n t s t o n e x u s 7 k - d o c f e e d b a c k @ c i s c o . c o m
Default UDLD Configuration
Table 2-4
Table 2-4
Feature
UDLD global enable state
UDLD per-port enable state for fiber-optic media
UDLD per-port enable state for twisted-pair (copper)
media
UDLD aggressive mode
UDLD message interval
For information on configuring the UDLD for the device and its port, see the
Mode" section on page
UDLD Aggressive and Nonaggressive Modes
UDLD aggressive mode is disabled by default. You can configure UDLD aggressive mode only on
point-to-point links between network devices that support UDLD aggressive mode. If UDLD aggressive
mode is enabled, when a port on a bidirectional link that has a UDLD neighbor relationship established
stops receiving UDLD frame, UDLD tries to reestablish the connection with the neighbor. After eight
failed retries, the port is disabled.
To prevent spanning tree loops, nonaggressive UDLD with the default interval of 15 seconds is fast
enough to shut down a unidirectional link before a blocking port transitions to the forwarding state (with
default spanning tree parameters).
When you enable the UDLD aggressive mode, the following occurs:
•
•
In these cases, the UDLD aggressive mode disables one of the ports on the link, which prevents traffic
from being discarded.
You enable the UDLD aggressive mode globally to enable that mode on all the fiber ports. You must
Note
enable the UDLD aggressive mode on copper ports on specified interfaces.
When a line card upgrade is being performed during an in-service software upgrade (ISSU) and some of
Tip
the ports on the line card are members of a Layer 2 port channel and are configured with UDLD
aggressive mode. If one of the remote ports is shutdown, UDLD puts the corresponding port on the local
device into error disabled state. This is correct behavior.
To restore service after the ISSU has completed, run a shutdown followed by a no shutdown command
on the local port.
OL-23435-03
shows the default UDLD configuration.
UDLD Default Configuration
2-39.
One side of a link has a port stuck (both transmission and receive)
One side of a link remains up while the other side of the link is down
Default Value
Globally disabled
Enabled on all Ethernet fiber-optic LAN ports
Disabled on all Ethernet 10/100 and
1000BASE-TX LAN ports
Disabled
15 seconds
Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x
Information About the Basic Interface Parameters
"Configuring the UDLD
2-9