HP Cisco Nexus 5000 Cisco Nexus 5000 Series Switch CLI Software Configuration - Page 113

Information About Ethernet Interfaces Default UDLD Configuration The following figure shows an example of a unidirectional link condition. Device B successfully receives traffic from Device A on the port. However, Device A does not receive traffic from Device B on the same port. UDLD detects the problem and disables the port. Figure 7: Unidirectional Link Default UDLD Configuration The following table shows the default UDLD configuration. Table 7: UDLD Default Configuration Feature UDLD global enable state Default Value Globally disabled UDLD aggressive mode Disabled UDLD per-port enable state for fiber-optic media Enabled on all Ethernet fiber-optic LAN ports UDLD per-port enable state for twisted-pair (copper) Disabled on all Ethernet 10/100 and 1000BASE-TX media LAN ports Related Topics • Configuring the UDLD Mode, page 69 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 frames, 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: • One side of a link has a port stuck (both transmission and receive) OL-16597-01 Cisco Nexus 5000 Series Switch CLI Software Configuration Guide 67