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Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
OL-23826-09
Chapter39 Remote Loop-Free Alternate - Fast Reroute
Contents
Prerequisites
• Cisco IOS Release 15.2(2)SNI or a later release that supports the Remote LFA-FRR feature must be
installed previously on the Cisco ASR 901 Series Aggregation Services Router.
• You should enable the following commands at the global configuration mode before configuring the
Remote LFA-FRR feature.
–
asr901-platf-frr enable
–
mpls label protocol ldp
–
mpls ldp router-id loopback-id force
–
mpls ldp discovery targeted-hello accept
–
no l3-over-l2 flush buffers
• Your network must support the following Cisco IOS features before you can enable fast reroute link
protection:
–
IP Cisco Express Forwarding (CEF)
–
Multiprotocol Label Switching (MPLS)
• Your network must also support at least one of the following protocols:
–
Intermediate System-to-Intermediate System (IS-IS)
–
Open Shortest Path First (OSPF)
• You should use throttle interior gateway protocol (IGP) timers for IS-IS and OSPF protocols.
Restrictions
• 4-label push is not supported. Due to this limitation, Labeled BGP access (RFC 3107) with Remote
LFA-FRR/TE-FRR is not supported, if it exceeds three labels. Four label push is observed on
L2VPN and L3VPN scenarios where multihop tunnel terminates before the destination. The four
labels are given below:
–
Backup-Repair Label
–
Tunnel Label
–
MPLS LDP Label
–
VC or VRF Label
• Since FRR is a software based solution on the Cisco ASR 901 router, you should keep the number
of prefixes, label-entries, and pseudowires to a minimum to obtain good convergence numbers.
• Remote LFA-FRR is not supported on layer 3 over layer 2 deployments. Disable this configuration
using the no l3-over-l2 flush buffers command before configuring Remote LFA-FRR.
• Ethernet over Multiprotocol Label Switching (EoMPLS) redundancy is not useful unless you have
dual home pseudowire and a protecting backup pseudowire egress link with FRR.
• Psuedowire redundancy over RLFA is supported effective with Cisco IOS Realease 15.4(1)S.
• TDM psuedowires over RLFA is supported effective with Cisco IOS Realease 15.3(3)S.
• CFM over Xconnect over TE-FRR is not supported.
• The imposition statistics do not work for EoMPLS after the FRR event or layer 3 cutover.