To ensure that existing network applications see no difference when a primary interface in a redundant
pair transitions to the backup interface, 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 no interface 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 previous illustration, interface 3/41 is a backup interface for 3/42, and 3/42 is in the
Down state. If 3/41 fails, 3/42 transitions to the Up state, which makes the backup link active. A message
similar to the following message appears whenever you configure a backup port.
02:28:04: %SYSTEM-P:CP %IFMGR-5-L2BKUP_WARN: Do not run any Layer2 protocols on
Te 3/41
and Te 3/42
02:28:04: %SYSTEM-P:CP %IFMGR-5-OSTATE_DN: Changed interface state to down: Te
3/42
02:28:04: %SYSTEM-P:CP %IFMGR-5-STATE_ACT_STBY: Changed interface state to
standby: Te
3/42
Example of Configuring Redundant Layer 2 Pairs
Dell(conf-if-range-te-3/41-42)#switchport backup interface TengigabitEthernet
3/42
Dell(conf-if-range-te-3/41-42)#show config
!
interface TengigabitEthernet 3/41
no ip address
switchport
switchport backup interface TengigabitEthernet 3/42
no shutdown
!
interface TengigabitEthernet 3/42
no ip address
switchport
no shutdown
Dell(conf-if-range-te-3/41-42)#
Dell(conf-if-range-te-3/41-42)#do show ip int brief | find 3/41
TengigabitEthernet 3/41 unassigned YES Manual up up
TengigabitEthernet 3/42 unassigned NO Manual up down
[output omitted]
Dell(conf-if-range-te-3/41-42)#interface tengig 3/41
Dell(conf-if-te-3/41)#shutdown
00:24:53: %SYSTEM-P:CP %IFMGR-5-ASTATE_DN: Changed interface Admin state to
down: Te 3/41
Dell(conf-if-te-3/41)#00:24:55: %SYSTEM-P:CP %IFMGR-5-OSTATE_DN: Changed
interface state to
down: Te 3/41
00:24:55: %SYSTEM-P:CP %IFMGR-5-INACTIVE: Changed Vlan interface state to
inactive: Vl 1
00:24:55: %SYSTEM-P:CP %IFMGR-5-OSTATE_UP: Changed interface state to up: Te
Layer 2 537