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.