Received label-unicast routes can be installed by BGP as tunnels in the tunnel table. In SR OS, the tunnel table is used to resolve a BGP next-hop to a tunnel when required by the configuration or the type of route (see Next-hop resolution). BGP tunnels play a key role in the following solutions:
inter-AS model C
carrier supporting carrier (CSC)
seamless MPLS
BGP tunnels have a preference of 10 in the tunnel table, compared to 9 for LDP tunnels and 7 for RSVP tunnels. If the router configuration allows all types of tunnels to resolve a BGP next-hop, an RSVP LSP is preferred over an LDP tunnel, and an LDP tunnel is preferred over a BGP tunnel.
Further details about BGP-LU tunnels depending on the address family, are described below.