gated.conf.4 (2010 09)

g
gated.conf(4) gated.conf(4)
restrict
Specifies that the routes are not desired in the routing table. In some cases this means that
the routes are not installed in the routing table. In others it means that they are installed with
a negative preference; this prevents them from becoming active so they will not be installed in
the forwarding table, or exported to other protocols.
preference preference
Specifies the preference value used when comparing this route to other routes from other pro-
tocols. The route with the lowest preference available at any given route becomes the active
route, is installed in the forwarding table, and is eligible to be exported to other protocols. The
default preferences are configured by the individual protocols.
Route Filters
All the formats allow route filters as shown below. See the section on route filters for a detailed explana-
tion of how they work. When no route filtering is specified (when restrict is specified on the first line
of a statement), all routes from the specified source will match that statement. If any filters are specified,
only routes that match the specified filters will be imported. Put differently, if any filters are specified, an
all restrict; is assumed at the end of the list.
network [ exact | refines ]
network mask mask [exact | refines ]
network masklen number [ exact | refines ]
default
host host
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 an 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. BGP version 4 supports the propagation of any destination
along with a contiguous network mask.
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 forward-
ing table, or exported to other protocols. This alleviates the need to break and re-establish a session upon
reconfiguration if importation policy is changed.
Importing routes from an RIP, HELLO and Redirects
import proto rip | hello | redirect
[(interface interface_list )|(gateway gateway_list )]
restrict ;
import proto rip | hello | redirect
[(interface interface_list )|(gateway gateway_list )]
[ preference preference ] {
route_filter [ restrict |(preference preference )];
};
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