Cisco NCS 6000 Series

CHAPTER 8
Implementing IP Fast Reroute Loop-Free
Alternate
IP Fast Reroute Loop-Free Alternate feature enables you to tunnel a packet around a failed link to a remote
loop-free alternate that is more than one hop away.
• Prerequisites for IPv4/IPv6 Loop-Free Alternate Fast Reroute, on page 345
• Restrictions for Loop-Free Alternate Fast Reroute, on page 345
• IS-IS and IP FRR, on page 346
• Repair Paths, on page 346
• LFA Overview, on page 347
• LFA Calculation, on page 347
• Interaction Between RIB and Routing Protocols, on page 347
• Configuring Fast Reroute Support, on page 348
• Configuring IPv4 Loop-Free Alternate Fast Reroute Support: Example, on page 350
• Additional References, on page 350
Prerequisites for IPv4/IPv6 Loop-Free Alternate Fast Reroute
• Loop-Free Alternate (LFA) Fast Reroute (FRR) can protect paths that are reachable through an interface
only if the interface is a point-to-point interface.
• When a LAN interface is physically connected to a single neighbor, you should configure the LAN
interface as a point-to-point interface so that it can be protected through LFA FRR.
Restrictions for Loop-Free Alternate Fast Reroute
• Load balance support is available for FRR-protected prefixes, but the 50 ms cutover time is not guaranteed.
• A maximum of eight FRR-protected interfaces can simultaneously undergo a cutover.
• Only Layer 3 VPN is supported.
• The remote LFA backup path for MPLS traffic can be setup only using LDP.
Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 6.4.x
345