Cisco WS-C2960-24PC-L Software Guide - Page 365
Specifying the UDLD Message Interval, Enabling UDLD Aggressive Mode
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Chapter 23 Configuring UDLD Configuring UDLD on the Switch Specifying the UDLD Message Interval To specify the UDLD message interval, perform this task in privileged mode: Step 1 Step 2 Task Specify the UDLD message interval. Verify the configuration. Command set udld interval interval show udld This example shows how to specify the UDLD message interval: Console> (enable) set udld interval 10 UDLD message interval set to 10 seconds Console> (enable) This example shows how to verify the message interval: Console> (enable) show udld UDLD : enabled Message Interval : 10 seconds Console> (enable) Enabling UDLD Aggressive Mode Software release 5.4(3) and later releases support UDLD aggressive mode. UDLD aggressive mode is disabled by default and its use is recommended only for point-to-point links between Cisco switches running software release 5.4(3) or later releases. With aggressive mode enabled, when a port on a bidirectional link stops receiving UDLD packets, UDLD tries to reestablish the connection with the neighbor. After eight failed retries, the port is put into errdisable state. To prevent spanning tree loops, normal UDLD with a 15-second message interval is fast enough to shut down a unidirectional link before a blocking port transitions to forwarding state (when default spanning tree parameters are used). Enabling UDLD aggressive mode provides additional benefits in the following cases: • One side of a link has a port stuck (both Tx and Rx) • One side of a link remains up while the other side of the link has gone down In these cases, UDLD aggressive mode error disables one of the ports on the link and stops the loss of traffic. Even with aggressive mode disabled, there is no risk for a broadcast storm due to a spanning tree loop in this situation, because one port cannot pass traffic in both directions. To enable UDLD aggressive mode on module ports, perform this task in privileged mode: Step 1 Step 2 Task Enable UDLD aggressive mode. Verify the configuration. Command set udld aggressive-mode enable mod_num/port_num show udld This example shows how to enable UDLD aggressive mode: Console> (enable) set udld aggressive-mode enable 4/1 Aggressive UDLD enabled on port 4/1. Console> (enable) 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 23-5
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