Cisco ASR 903 Guide

LFA & Remote LFA (rLFA)
BFD Triggered TE Fast Reroute ▀
Cisco ASR 903 Router Design and Deployment Guide▄
OL-30526-01
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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)

Cisco ASR 903 Specifications

General

Form Factor	Modular
Storage Temperature	-40°C to 70°C (-40°F to 158°F)
Humidity	5% to 95% non-condensing
Redundancy	Yes, redundant power supplies and route processors
Operating System	Cisco IOS XE
Power Supply	AC or DC
Switching Capacity	240 Gbps
Operating Temperature	-40°C to 65°C (-40°F to 149°F)
MTBF	200, 000 hours
Supported Protocols	IPv4, IPv6, MPLS, L2VPN, L3VPN
Interfaces	Gigabit Ethernet, 10 Gigabit Ethernet, T1/E1