HP-UX Reference (11i v2 03/08) - 4 File Formats (vol 8)

g
gated.conf(4) gated.conf(4)
Route aggregation is also used by regional and national networks to reduce the amount of routing infor-
mation passed around. With careful allocation of network addresses to clients, regional networks can just
announce one route to regional networks instead of hundreds.
Aggregate routes are not actually used for packet forwarding by the originator of the aggregate route,
only by the receiver (if it wishes). A router receiving a packet which does not match one of the component
routes which led to the generation of an aggregate route is supposed to respond with an ICMP network
unreachable message. This is to prevent packets for unknown component routes from following a default
route into another network where they would be forwarded back to the border router, and around and
around again and again, until their TTL expires. Sending an unreachable message for a missing piece of
an aggregate is only possible on systems with support for reject routes.
A slight variation of aggregation is the generation of a route based on the existence of certain conditions.
This is sometimes known as the route of last resort. This route inherits the next hops and aspath from the
contributor specified with the lowest (most favorable) preference. The most common usage for this is to
generate a default based on the presence of a route from a peer on a neighboring backbone.
Aggregation and Generation syntax
aggregate default
|(network [(mask mask )|(masklen number )])
[ preference preference ][brief ] {
proto [ all | direct | static | kernel | aggregate | proto ]
[(as autonomous system )|(tag tag )
|(aspath aspath_regexp )]
restrict ;
proto [ all | direct | static | kernel | aggregate | proto ]
[(as autonomous system )|(tag tag )
|(aspath aspath_regexp )]
[ preference preference ] {
route_filter [ restrict |(preference preference )];
};
};
generate default
|(network [(mask mask )|(masklen number )])
[ preference preference ] {
[(as autonomous system )|(tag tag )
|(aspath aspath_regexp )]
restrict ;
proto [ all | direct | static | kernel | aggregate | proto ]
[(as autonomous system )|(tag tag )
|(aspath aspath_regexp )]
[ preference preference ] {
route_filter [ restrict |(preference preference )];
};
};
Routes that match the route filters are called contributing routes. They are ordered according to the
aggregation preference that applies to them. If there are more than one contributing routes with the same
aggregating preference, the preferences of the route are used to order the routes. The preference of the
aggregate route will be that of the contributing route with the lowest aggregate preference.
preference preference
Specifies the preference to assign to the resulting aggregate route. The default preference is
130.
brief
Used to specify that the AS path should be truncated to the longest common AS path. The
default is to build an AS path consisting of SETs and SEQUENCEs of all contributing AS
paths.
proto proto
In addition to the special protocols listed, the contributing protocol may be chosen from among
any of the ones supported (and currently configured into) GateD.
HP-UX 11i Version 2: August 2003 − 49 − Hewlett-Packard Company Section 4−−125