BFD Triggered TE Fast Reroute ▀
Cisco ASR 903 Router Design and Deployment Guide▄
Chapter 8 LFA & Remote LFA (rLFA)
When a link or a router fails, distributed routing algorithms compute new routes that take into account the failure.
The time taken for computation is called routing transition. Until the transition is complete and all routers are
converged on a common view of the network, the connectivity between the source and destination pairs is
interrupted. IPv4 Loop-Free Alternate (LFA) Fast Reroute (FRR) feature can reduce the routing transition time to
less than 50 milliseconds using a pre-computed alternate next hop. When a router is notified of a link failure, the
router immediately switches over to the repair path to reduce traffic loss.
IPv4 LFA FRR supports the pre-computation of repair paths. The repair path computation can be done by IS-IS or
OSPF routing protocol, and the resulting repair paths are sent to the RIB.
Figure 25. LFA
Gi 0/2/3
Gi 0/2/3
Gi 0/2/1
Gi 0/2/0
Gi 0/2/0
Gi 0/2/2
Gi 0/2/0
Gi 0/2/2
10.10.1.x
10.10.2.x
10.10.4.x
10.10.5.x
ASR903-R2
(172.16.2.2)
ASR903-R1
(172.16.1.1)
ASR903-R3
(172.16.3.3)
ASR903-R4
(172.16.4.4)
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