Configuring Ethernet Link Redundancy

To configure Ethernet link redundancy:

1. Specify the Fast Ethernet or Gigabit Ethernet interface on which to configure a redundant link.
   host1(config)#interface gigabitEthernet 1/1
2. For LAG to non-LAG configurations only, specify that LACP is disabled on the port.
   host1(config-if)#no lacp
3. Configure a backup interface and disable LACP on it.
   host1(config)#interface gigabitEthernet 1/0 host1(config-if)#no lacp
4. Configure a LAG interface and assign a member link to the backup interface.
   host1(config)#interface lag myBundle host1(config-if)#member-interface gigabitEthernet 1/0 host1(config-if)#member-interface gigabitEthernet 1/1
5. Do one of the following:
   • Configure link redundancy on the port you specified in step  1.
     host1(config-if)#redundant-port gigabitEthernet 1/1
   • Force the port you specified in step 1 to fail over.
     host1(config-if)#redundant-port gigabitEthernet 1/1 force-failover
6. (Optional) Configure the redundant link to revert back to redundant mode when the failed link becomes active again.
   host1(config-if)#redundant-port gigabitEthernet 1/1 auto-revert

Note: In JunosE Release 12.1.x and lower-numbered releases, if you shut down the member interface in a LAG bundle and clear the ARP entry associated with that member link, ARP does not work correctly when the active link encounters a fault and fails over to the redundant link in the LAG bundle. This problem occurs because the forwarding controller incorrectly sends an exception for the channel ID to the interface controller for member interfaces in the LAG bundle configured with the redundant-port command that fail over to other links in the LAG bundle. Beginning with JunosE Release 12.2.x, ARP works correctly for member links in the LAG bundle that are configured as redundant interfaces when they encounter a failure and fails over to other links in the LAG bundle.