To ensure that existing network applications see no difference when a primary interface in a redundant pair transitions to the backupinterface, be sure to apply identical configurations of other traffic parameters to each interface.If you remove an interface in a redundant link (remove the line card of a physical interface or delete a port channel with the nointerface port-channel command), the redundant pair configuration is also removed.Important Points about Configuring Redundant Pairs• You may not configure any interface to be a backup for more than one interface, no interface can have more than one backup,and a backup interface may not have a backup interface.• The active or backup interface may not be a member of a LAG.• The active and standby do not have to be of the same type (1G, 10G, and so on).• You may not enable any Layer 2 protocol on any interface of a redundant pair or to ports connected to them.As shown in the above illustration, interface 3/41 is a backup interface for 3/42, and 3/42 is in the Down state. If 3/41 fails, 3/42transitions to the Up state, which makes the backup link active. A message similar to the following message appears whenever youconfigure a backup port.02:28:04: %RPM0-P:CP %IFMGR-5-L2BKUP_WARN: Do not run any Layer2 protocols on Te 3/41 andTe 3/4202:28:04: %RPM0-P:CP %IFMGR-5-OSTATE_DN: Changed interface state to down: Te 3/4202:28:04: %RPM0-P:CP %IFMGR-5-STATE_ACT_STBY: Changed interface state to standby: te 3/42Example of Configuring Redundant Layer 2 PairsDell(conf-if-range-te-3/41-42)#switchport backup interface TenGigabitEthernet 3/42Dell(conf-if-range-te-3/41-42)#show config!interface TenGigabitEthernet 3/41no ip addressswitchportswitchport backup interface TenGigabitEthernet 3/42no shutdown!interface TenGigabitEthernet 3/42no ip addressswitchportno shutdownDell(conf-if-range-te-3/41-42)#Dell(conf-if-range-te-3/41-42)#do show ip int brief | find 3/41TenGigabitEthernet 3/41 unassigned YES Manual up upTenGigabitEthernet 3/42 unassigned NO Manual up down[output omitted]Dell(conf-if-range-te-3/41-42)#interface tengig 3/41Dell(conf-if-te-3/41)#shutdown00:24:53: %RPM0-P:CP %IFMGR-5-ASTATE_DN: Changed interface Admin state to down: Te 3/41Dell(conf-if-te-3/41)#00:24:55: %RPM0-P:CP %IFMGR-5-OSTATE_DN: Changed interface state todown: Te 3/4100:24:55: %RPM0-P:CP %IFMGR-5-INACTIVE: Changed Vlan interface state to inactive: Vl 100:24:55: %RPM0-P:CP %IFMGR-5-OSTATE_UP: Changed interface state to up: Te 3/4200:24:55: %RPM0-P:CP %IFMGR-5-ACTIVE: Changed Vlan interface state to active: Vl 100:24:55: %RPM0-P:CP %IFMGR-5-STATE_STBY_ACT: Changed interface state from standby toactive:Te 3/42Dell(conf-if-te-3/41)#do show ip int brief | find 3/41TenGigabitEthernet 3/41 unassigned NO Manual administratively down downTenGigabitEthernet 3/42 unassigned YES Manual up up[output omitted]Example of Configuring Redundant Pairs on a Port-ChannelDell#show interfaces port-channel briefCodes: L - LACP Port-channelLAG Mode Status Uptime Ports1 L2 up 00:08:33 Te 1/1 (Up)490 Layer 2
