Ospf Routes - HP procurve 8100fl series Management And Configuration Manual

OSPF Configuration
Overview
N o t e
13-4
Area Routers. In connection to areas, the following terms are used in OSPF:
■ ABR (Area Border Router) — A router that connects the Backbone (area
0) with some other area(s).
ASBR (Autonomous System Border Router) —A router that redistributes
■
routes in OSPF (from connected, statics, or another routing protocol). An
ASBR can exist in the Backbone area, or in any other non-stub area.

OSPF Routes

Once areas have been configured, four types of OSPF routes can be
encountered in the network. They are in order of preference:
■ Intra-area routes—represent destinations within the same area
Inter-area routes—reflect destinations from other OSPF areas
■
External Type 1 routes
■
■ External Type 2 routes
External routes. Both types of External routes represent destinations that
are outside of the OSPF routing domain. These routes were injected into OSPF
via redistribution, either from static or direct (connected) or from another
routing protocol.
The difference between the two types of Externals is in the way their cost is
calculated as routes are propagated within the OSPF domain.
In both types, Externals are redistributed by an ASBR within the OSPF
■
domain. The ASBR always redistributes routers with a given cost.
■ For Type 1 Externals, the given redistribution cost is added to the OSPF
link costs as the route is propagated downstream. As a result, the cost of
a Type 1 route will increase as the route travels downstream in the OSPF
domain.
The redistribution cost of a Type 2 External does not change as the route
■
is propagated down the OSPF domain.
By default, the ProCurve 8100fl redistributes Type 2 Externals.