Riverstone Networks WICT1-12 - Manual (Page 436)

18-6 Riverstone Networks RS Switch Router User Guide Release 8.0
Preference Routing Policy Configuration
• Route-Filter
Aggregate-Destination
This component specifies the aggregate/summarized route. It also specifies the attributes associated with the aggregate
route. The preference to be associated with an aggregate route can be specified using this component.
Aggregate-Source
This component specifies the source of the routes contributing to an aggregate/summarized route. It can also specify
the preference to be associated with the contributing routes from this source. This preference can be overridden by
explicitly specifying a preference with the route-filter.
The routes contributing to an aggregate can be identified by their associated attributes:
• Protocol type (RIP, OSPF, BGP, Static, Direct, Aggregate, IS-IS).
• Autonomous system from which the route was learned.
• AS path associated with a route. When BGP is configured, all routes are assigned an AS path when
they are added to the routing table. For interior routes, this AS path specifies IGP as the origin and
no ASs in the AS path (the current AS is added when the route is exported). For BGP routes, the AS
path is stored as learned from BGP.
• Tag associated with a route. Both OSPF and RIP version 2 currently support tags. All other protocols
have a tag of zero.
In some cases, a combination of the associated attributes can be specified to identify the routes contributing to an
aggregate.
Route-Filter
This component specifies the individual routes that are to be aggregated or summarized. The preference to be
associated with these routes can also be explicitly specified using this component.
The contributing routes are ordered according to the aggregation preference that applies to them. If there is more than
one contributing route with the same aggregating preference, the route's own preferences are used to order the routes.
The preference of the aggregate route will be that of contributing route with the lowest aggregate preference.
A route may only contribute to an aggregate route that is more general than itself; it must match the aggregate under
its mask. Any given route may only contribute to one aggregate route, which will be the most specific configured, but
an aggregate route may contribute to a more general aggregate.
An aggregate-route only comes into existence if at least one of its contributing routes is active.
18.1.5 Authentication
Authentication guarantees that routing information is only imported from trusted routers. Many protocols like RIP V2
and OSPF provide mechanisms for authenticating protocol exchanges. A variety of authentication schemes can be
used. Authentication has two components – an Authentication Method and an Authentication Key. Many protocols
allow different authentication methods and keys to be used in different parts of the network.