Networking Guide
Chapter 5, Configuring Internet Protocol (IP) routing

Importing routes from BGP and EGP

Importing routes from BGP and EGP



   import proto bgp | egp autonomoussystem autonomous_system
       restrict ;
   import proto bgp | egp autonomoussystem autonomous_system
       [ preference preference ] {
       route_filter [ restrict | ( preference preference ) ] ;
   } ;
   

import proto bgp aspath aspath_regexp origin any | ( [ igp ] [egp ] [ incomplete ] ) restrict ; import proto bgp aspath aspath_regexp origin any | ( [ igp ] [egp ] [ incomplete ] ) [ preference preference ] { route_filter [ restrict | ( preference preference ) ] ; } ;

EGP importation may be controlled by autonomous_system. BGP also supports controlling propagation by the use of AS path regular expressions, which are documented in the section on matching AS paths. Note that EGP and BGP Versions 2 and 3 only support the propagation of natural networks, so the host and default route filters are meaningless.

EGP and BGP both store any routes that were rejected implicitly by not being mentioned in a route filter or explicitly with the restrict keyword in the routing table with a negative preference. A negative preference prevents a route from becoming active, which prevents it from being installed in the forwarding table or exported to other protocols. This alleviates breaking and reestablishing a session upon reconfiguration if importation policy is changed.