Family prefix resolution and tunnel selection rules

The following are the details of the resolution of prefix families in the unicast and multicast routing tables:

• family srv4 enables the resolution of SR-OSPF IPv4 tunnels and SR-ISIS IPv4 tunnels in MT=0 over RSVP-TE IPv4 IGP shortcuts. A maximum of 32 ECMP tunnel next hops can be programmed for an SR-OSPF or an SR-ISIS IPv4 tunnel.

• family srv6 enables the resolution of SR-ISIS IPv6 tunnels in MT=0 over RSVP-TE IPv4 IGP shortcuts. A maximum of 32 ECMP tunnel next hops can be programmed for an SR-ISIS IPv6 tunnel.

  Note: Segment routing is not supported in IS-IS MT=2.

• One or more RSVP-TE LSPs can be selected if resolution is set to match-family-ip and the corresponding IPv4 or IPv6 prefix is resolved to RSVP-TE LSPs.

• An SR tunnel cannot resolve to SR-TE IGP shortcuts. If resolution is set to match-family-ip and the corresponding IPv4 or IPv6 prefix is resolved to SR-TE LSPs, the SR tunnel is resolved to IP next hops in the multicast routing table.

• For an SR tunnel corresponding to an inter-area prefix with best routes via multiple ABRs, setting resolution to match-family-ip means the SR tunnel can resolve to RSVP-TE LSPs to one or more ABR nodes. If, however, only SR-TE LSPs exist to any of the ABR nodes, IGP does not include this ABR in the selection of ECMP next hops for the tunnel. If there exists no RSVP-TE LSPs to all ABR nodes, the inter-area prefix is resolved to IP next hops in the multicast routing table.

  Note: While this feature is intended to tunnel SR-ISIS IPv4 and IPv6 tunnels and SR-OSPF IPv4 tunnels over RSVP-TE IPv4 IGP shortcuts, an SR-TE LSP that has its first segment (ingress LER role) or its next segment (LSR role) correspond to one of these SR-ISIS or SR-OSPF tunnels is also tunneled over RSVP-TE LSP.

• resolution disabled is the default value for the srv4 and srv6 families and means that SR-ISIS and SR-OSPF tunnels are resolved to IP links in the multicast routing table.