Technical data

Gateway Routing Daemon (GATED) Configuration Reference
A.18 Control Statements
import proto bgp aspath aspath_regexp
origin any | ( [ igp ] [egp ] [ incomplete ] )
[ aspath-opt ] restrict ;
import proto bgp aspath aspath_regexp
origin any | ( [ igp ] [egp ] [ incomplete ] )
[ aspath-opt ] [ 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.
The
aspath-opt option allows the specification of import policy based on the
path attributes found in the BGP update. (The option is not usable with EGP.)
If multiple communities are specified in the aspath-opt option, only updates
carrying all of the specified communities will be matched. If none is specified,
only updates lacking the community attribute will be matched.
Note that it is quite possible for several BGP import clauses to match a given
update. If more than one clause matches, the first matching clause will be
used; all later matching clauses will be ignored. For this reason, it is generally
desirable to order import clauses from most to least specific. An import clause
without an
aspath-opt option will match any update with any communities or
none.
EGP and BGP both store any routes that were rejected implicitly by not being
metioned 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 aleviates the need to break and re-establish a
session upon reconfiguration if importation policy is changed.
A.18.3.4 Importing Routes from RIP and Redirects
Use the following syntax to define importing routes from RIP and redirect routes:
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 )];
};
The importation of RIP and redirect routes may be controlled by any of protocol,
source interface and source gateway. If more than one is specified, they are
processed from most general (protocol) to most specific (gateway).
RIP does not support the use of preference to choose between routes of the same
protocol. That is left to the protocol metrics. These protocols do not save routes
that were rejected since they have short update intervals.
A–36 Gateway Routing Daemon (GATED) Configuration Reference