Configuration

Since TI-LFA leverages the IGP for computing backup routes, its activation in the Cisco IOS-XR software involves applying two essential commands to the physical interfaces of the IS-IS link-state routing protocol.

The fast-reroute per-prefix command exclusively enables classic LFA. Subsequently, the fast-reroute per-prefix ti-lfa command, added after the previous one, activates TI-LFA.

Both commands are essential for enabling TI-LFA protection, and this process is shown further as follows:

• The PE1 router is connected only to P2, so TI-LFA is activated on that specific interface under the IS-IS configuration context:

  PE1

  router isis IGP
  interface GigabitEthernet0/0/0/2
    address-family ipv4 unicast
     fast-reroute per-prefix
     fast-reroute per-prefix ti-lfa

• On the P2 router, TI-LFA is activated on the interfaces connected to PE1, P3, P6, and P7, as shown here:

  P2

  router isis IGP
  interface GigabitEthernet0/0/0/0
   ...