Layer 2 | 531Enable and Disable VLAN Flooding• ARP entries already resolved through the VLAN are deleted when the feature is enabled. This ensuresthat ARP entries across the VLAN are consistent.• All ARP entries learned after the feature is enabled are deleted when the feature is disabled, and RP2triggers ARP resolution. The feature is disabled with the command no vlan-flooding.• When a port is added to the VLAN, the port automatically receives traffic if the feature is enabled. OldARP entries are not deleted or updated.• When a member port is deleted, its ARP entries are also deleted from the CAM.• Port channels in the VLAN also receive traffic.• There is no impact on the configuration from saving the configuration.• The feature is not reflected in the output of the show arp command but is reflected in the output of thecommand show ipf fib.The ARP entries exist in the secondary RPM CAM, so failover has no effect on the feature.Configuring Redundant PairsConfiguring Redundant Pairs is supported on platforms: e c s zNetworks that employ switches that do not support Spanning Tree (STP)—for example, networks withDigital Subscriber Line Access Mutiplexers (DSLAM)—cannot have redundant links between switchesbecause they create switching loops (Figure 24-7). The Redundant Pairs feature enables you to createredundant links in networks that do not use STP by configuring backup interfaces for the interfaces oneither side of the primary link.Assign a backup interface to an interface using the command switchport backup. The backup interfaceremains in down state until the primary fails, at which point it transitions to up state. If the primaryinterface fails, and later comes up, it becomes the backup interface for the redundant pair. FTOS supportsGigabit, 10-Gigabit, and 40-Gigabit interfaces as backup interfaces.You must apply all other configurations to each interface in the redundant pair such that theirconfigurations are identical, so that transition to the backup interface in the event of a failure is transparentto rest of the network.Note: For details on STP, see Chapter 44, “Spanning Tree Protocol (STP),” on page 875.
