BGP fast reroute is a feature that brings together indirection techniques in the forwarding plane and pre-computation of BGP backup paths in the control plane to support fast reroute of BGP traffic around unreachable/failed next-hops. In a VPRN context BGP fast reroute is supported using unlabeled IPv4, unlabeled IPv6, VPN-IPv4, and VPN-IPv6 VPN routes. The supported VPRN scenarios are described in Table: BGP fast reroute scenarios (VPRN context).
BGP fast reroute information specific to the base router BGP context is described in the BGP Fast Reroute section of the 7450 ESS, 7750 SR, 7950 XRS, and VSR Unicast Routing Protocols Guide.
| Ingress packet | Primary route | Backup route | Prefix independent convergence |
|---|---|---|---|
IPv4 (ingress PE) |
IPv4 route with next-hop A resolved by an IPv4 route |
IPv4 route with next-hop B resolved by an IPv4 route |
Yes |
IPv4 (ingress PE) |
VPN-IPv4 route with next-hop A resolved by a GRE, LDP, RSVP or BGP tunnel |
VPN-IPv4 route with next-hop A resolved by a GRE, LDP, RSVP or BGP tunnel |
Yes |
MPLS (egress PE) |
IPv4 route with next-hop A resolved by an IPv4 route |
IPv4 route with next-hop B resolved by an IPv4 route |
Yes |
MPLS (egress PE) |
IPv4 route with next-hop A resolved by an IPv4 rout |
VPN-IPv4 route* with next-hop B resolved by a GRE, LDP, RSVP or BGP tunnel |
Yes |
IPv6 (ingress PE) |
IPv6 route with next-hop A resolved by an IPv6 route |
IPv6 route with next-hop B resolved by an IPv6 route |
Yes |
IPv6 (ingress PE) |
VPN-IPv6 route with next-hop A resolved by a GRE, LDP, RSVP or BGP tunnel |
VPN-IPv6 route with next-hop B resolved by a GRE, LDP, RSVP or BGP tunnel |
Yes |
MPLS (egress) |
IPv6 route with next-hop A resolved by an IPv6 route |
IPv6 route with next-hop B resolved by an IPv6 route |
Yes |
MPLS (egress) |
IPv6 route with next-hop A resolved by an IPv6 route |
Yes |
VPRN label mode must be VRF. VPRN must export its VPN-IP routes with RD ≠ y. For the best performance the backup next-hop must advertise the same VPRN label value with all routes (per VRF label). |