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 abackup 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 previous illustration, interface 1/1/1/1 is a backup interface for 1/1/2/1, and 1/1/3/1 is in the Down state. If 1/1/1/1 fails,1/1/2/1 transitions 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 1/1/1/1 and Te1/1/1/202:28:04: %RPM0-P:CP %IFMGR-5-OSTATE_DN: Changed interface state to down: Te 1/1/1/202:28:04: %RPM0-P:CP %IFMGR-5-STATE_ACT_STBY: Changed interface state to standby: te 1/1/1/2Example of Configuring Redundant Layer 2 PairsDell(conf-if-range-te-1/1/1/1-1/1/1/2)#switchport backup interface TenGigabitEthernet 1/1/1/2Dell(conf-if-range-te-1/1/1/1-1/1/1/2)#show config!interface TenGigabitEthernet 1/1/1/1no ip addressswitchportswitchport backup interface TenGigabitEthernet 1/1/1/2no shutdown!interface TenGigabitEthernet 1/1/1/2no ip addressswitchportno shutdownDell(conf-if-range-te-1/1/1/1-1/1/1/2)#Dell(conf-if-range-te-1/1/1/1-1/1/1/2)#do show ip int brief | find 1/1/1/2TenGigabitEthernet 1/1/1/1 unassigned YES Manual up upTenGigabitEthernet 1/1/1/1 unassigned NO Manual up down[output omitted]Dell(conf-if-range-te-1/1/1/1-1/1/1/2)#interface TenGigabitEthernet 1/1/1/1Dell(conf-if-te-1/1/1/2)#shutdown00:24:53: %RPM0-P:CP %IFMGR-5-ASTATE_DN: Changed interface Admin state to down: Te 1/1/1/2Dell(conf-if-te-1/1/1/1)#00:24:55: %RPM0-P:CP %IFMGR-5-OSTATE_DN: Changed interface state todown: Te 1/1/1/200:24:55: %RPM0-P:CP %IFMGR-5-INACTIVE: Changed Vlan interface state toinactive: Vl 100:24:55: %RPM0-P:CP %IFMGR-5-OSTATE_UP: Changed interface state to up: Te 1/1/1/100:24:55: %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 to active:Te 1/1/1/2Dell(conf-if-te-1/1/1/1)#do show ip int brief | find 1/1/1/2TenGigabitEthernet 1/1/1/1 unassigned NO Manual administratively down downTenGigabitEthernet 1/1/1/2 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 1/1/1/1 (Up)2 L2 up 00:00:02 Te 1/1/1/2 (Up)Dell#configureDell(conf)#interface port-channel 1Dell(conf-if-po-1)#switchport backup interface port-channel 2Apr 9 00:15:13: %STKUNIT0-M:CP %IFMGR-5-L2BKUP_WARN: Do not run any Layer2 protocols on Po 1and Po 2Layer 2 487
