Route Types - HP 6125XLG Configuration Manual

Internal router—All interfaces on an internal router belong to one OSPF area.
•
• ABR—Belongs to more than two areas, one of which must be the backbone area. ABR connects the
backbone area to a non-backbone area. An ABR and the backbone area can be connected
through a physical or logical link.
Backbone router—At least one interface of a backbone router must reside in the backbone area.
•
All ABRs and internal routers in area 0 are backbone routers.
ASBR—Exchanges routing information with another AS is an ASBR. An ASBR might not reside on
•
the border of the AS. It can be an internal router or an ABR.
Figure 17 OSPF router types
Area 1
Internal router

Route types

OSPF prioritizes routes into the following route levels:
Intra-area route
•
Inter-area route
•
Type- 1 external route
•
• Type-2 external route
The intra-area and inter-area routes describe the network topology of the AS. The external routes describe
routes to external ASs.
A Type- 1 external route has high credibility. The cost from a router to the destination of a Type- 1 external
route = the cost from the router to the corresponding ASBR + the cost from the ASBR to the destination of
the external route.
A Type-2 external route has low credibility. OSPF considers the cost from the ASBR to the destination of
a Type-2 external route is much greater than the cost from the ASBR to an OSPF internal router. The cost
from the internal router to the destination of the Type-2 external route = the cost from the ASBR to the
RIP
IS-IS
ASBR
Area 0
ABR
Area 2
52
Area 4
Backbone router
Area 3