H3C Technologies H3C S7500E Series Switches - Manual (Page 76)

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z Compared with an NSSA area, a totally NSSA area does not import inter-area routes.
Router Types
Classification of Routers
The OSPF routers fall into four types according to 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 be attached to the backbone area. Therefore, all
ABRs and internal routers in area 0 are backbone routers.
4) Autonomous System Border Router (ASBR)
A router exchanging routing information with another AS is an ASBR, which may not reside on the
boundary of the AS. It can be an internal router or an ABR.
Figure 4-6 OSPF router types
Route types
OSPF prioritize routes into four levels:
z Intra-area route
z Inter-area route
z Type-1 external route
z Type-2 external route