Next-hop resolution of BGP labeled routes to tunnels

Use the following CLI syntax to configure next-hop resolution of BGP labeled routes.

CLI syntax:

config>router>bgp>next-hop-res
  labeled-routes
    transport-tunnel
      [no] family {label-ipv4|label-ipv6|vpn}
        resolution {any | disabled | filter}
        resolution-filter
          [no] bgp
          [no] ldp
	   [no] rsvp
	   [no] sr-isis
	   [no] sr-ospf
	   [no] sr-te
	   [no] udp

The transport-tunnel context provides separate control for the different types of BGP label routes: label-IPv4, label-IPv6, and VPN routes (which includes both VPN-IPv4 and VPN-IPv6 routes). By default, all labeled routes resolve to LDP (even if the preceding CLI commands are not configured in the system).

If the resolution option is set to disabled, the default binding to LDP tunnels resumes. If resolution is set to any, the supported tunnel type selection is based on TTM preference. The order of preference of TTM tunnels is: RSVP, SR-TE, LDP, segment routing OSPF, segment routing IS-IS, and UDP.

The rsvp option instructs BGP to search for the best metric RSVP LSP to the address of the BGP next-hop. The address can correspond to the system interface or to another loopback used by the BGP instance on the remote node. The LSP metric is provided by MPLS in the tunnel table. In the case of multiple RSVP LSPs with the same lowest metric, BGP selects the LSP with the lowest tunnel ID.

The ldp option instructs BGP to search for an LDP LSP with a FEC prefix corresponding to the address of the BGP next-hop.

The bgp option instructs BGP to search for a BGP tunnel in TTM with a prefix matching the address of the BGP next-hop. A label-unicast IPv4 route cannot be resolved by another label-unicast IPv4 or IPv6 route. A label-unicast IPv6 route cannot be resolved by another label-unicast IPv6 route, but it can be resolved by a label-unicast IPv4 route.

When the sr-isis or sr-ospf option is enabled, an SR tunnel to the BGP next-hop is selected in the TTM from the lowest preference IS-IS or OSPF instance. If many instances have the same lowest preference, the lowest numbered IS-IS or OSPF instance is chosen.

The sr-te value launches a search for the best metric SR-TE LSP to the address of the BGP next-hop. The LSP metric is provided by MPLS in the tunnel table. In the case of multiple SR-TE LSPs with the same lowest metric, BGP selects the LSP with the lowest tunnel-id.

The udp value instructs BGP to look for an MPLSoUDP tunnel to the address of the BGP next-hop.

If one or more explicit tunnel types are specified using the resolution-filter option, then only these tunnel types are selected again following the TTM preference. The resolution command must be set to filter to activate the list of tunnel-types configured in resolution-filter.