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Router types
Classification of routers
The following are OSPF router types and their positions in the AS:
1.
Internal router
All interfaces on an internal router belong to one OSPF area.
2.
Area Border Router (ABR)
An ABR belongs to more than two areas, one of which must be the backbone area. It connects the
backbone area to a non-backbone area. The connection between an ABR and the backbone area can
be physical or logical.
3.
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.
4.
Autonomous System Boundary Router (ASBR)
A router exchanging routing information with another AS is an ASBR, which may not reside on the border
of the AS. It can be an internal router or an ABR.
Figure 22
OSPF router types
Route types
OSPF prioritize routes into the following levels:
•
Intra-area route
•
Inter-area route
•
Type-1 external route
•
Type-2 external route
