BGP shortcuts configuration over segment routing tunnels

When you have segment routing enabled in your network, you can specify a segment routing tunnel as the next hop for a BGP route. This capability is referred to as BGP shortcuts over segment routing.

To configure BGP shortcuts, you must configure the BGP protocol with the allowed tunnel types and the required tunnel resolution mode.

Configuring BGP shortcuts

To configure BGP shortcuts, you must configure the BGP protocol in the default network-instance with the allowed tunnel types for next-hop resolution. You must also define the tunnel resolution mode, which determines the order of preference and the fallback when using tunnels in the tunnel table instead of routes in the FIB. Available options are as follows:

  • require: requires tunnel table lookup instead of FIB lookup
  • prefer: prefers tunnel table lookup over FIB lookup
  • disabled (default): performs FIB lookup only

Configure BGP next-hop resolution to allow segment routing tunnels

The following example shows the BGP next-hop resolution configuration to allow SR-ISIS tunnels, with the tunnel mode set to prefer. 

--{ * candidate shared default }--[ ]--
# info network-instance default protocols bgp ipv4-unicast next-hop-resolution ipv4-next-hops tunnel-resolution
    network-instance default {
        protocols {
            bgp {
                ipv4-unicast {
                    next-hop-resolution {
                        ipv4-next-hops {
                            tunnel-resolution {
                                mode prefer
                                allowed-tunnel-types [
                                    sr-isis
                                ]
                            }
                        }
                    }
                }
            }
        }
    }