To enable the next-hop resolution of unlabeled IPv6 routes using tunnels in the tunnel-table of the router, it is necessary to add family ipv6 under the config>router>bgp>next-hop-resolution>shortcut-tunnel context. If the next-hop of the IPv6 BGP route contains an IPv4-mapped IPv6 address, the shortcut-tunnel configuration applies to the use of IPv4 tunnels and IPv4 routes that match the embedded IPv4 address in the BGP next-hop. If the BGP next-hop is any other IPv6 address the shortcut-tunnel configuration applies to the use of IPv6 tunnels and IPv6 routes that match the full address of the BGP next-hop.
The family ipv6 context provides commands to specify the resolution mode (any, disabled or filter) and the set of tunnel types that are eligible for use if the filter mode (resolution filter) is selected.
If there are multiple tunnels in tunnel-table that are allowed by resolution any or resolution filter mode and that can resolve the BGP next-hop, the selection of the resolving tunnel is determined by factors such as route color, admin-tag-policy, tunnel-table preference, and LDP FEC prefix length.
If the resolution mode is set to disabled, the next-hops of unlabeled IPv6 routes can only be resolved by route table lookup.
If disallow-igp is enabled and no resolving tunnel is found in the tunnel table, no attempt is made to resolve the IPv6 BGP route using route table lookup.
The available tunneling options for IPv6 BGP routes with IPv4-mapped IPv6 next-hops are as follows:
bgp
This refers to IPv4 tunnels created by receiving BGP label-unicast IPv4 routes for /32 IPv4 prefixes.
ldp
This refers to /32 and shorter length LDP FEC prefixes imported into the tunnel table. For resolution purposes, BGP selects the LDP FEC that is the longest-prefix-match (LPM) of the BGP next-hop address.
rsvp
This refers to RSVP tunnels in tunnel-table. This option allows BGP to use the best metric RSVP LSP to the address of the BGP next-hop. This address can correspond to the system interface or to another loopback interface of the remote BGP router. In the case of multiple RSVP LSPs with the same lowest metric, BGP selects the LSP with the lowest tunnel-id.
sr-isis
This refers to segment routing tunnels (shortest path) to destinations reachable by the IS-IS protocol. This option allows BGP to use the segment routing tunnel in tunnel-table submitted by the lowest preference IS-IS instance or (in case of a tie) the lowest numbered IS-IS instance.
sr-ospf
This refers to segment routing tunnels (shortest path) to destinations reachable by the OSPF protocol. This option allows BGP to use the segment routing tunnel in tunnel-table submitted by the lowest preference OSPF instance or (in case of a tie) the lowest numbered OSPF instance.
sr-policy
This refers to segment routing policies that are statically configured in the local router or learned via BGP routes (AFI 1/SAFI 73). For BGP to resolve the next-hop of an IPv4 route using an sr-policy the highest numbered color-extended community attached to the IPv4 route must match the color of the SR policy and if the CO bits of this color -extended community have the value 00 the BGP next-hop of the route must exactly match the endpoint of the SR policy.
sr-te
This refers to TE segment routing tunnels. This option allows BGP to use the best metric SR-TE tunnel to the address of the BGP next-hop. In the case of multiple SR-TE tunnels with the same lowest metric, BGP selects the tunnel with the lowest tunnel-id.