Classification Of Routers - HP 4800G Series Configuration Manual

On the left of the figure, RIP routes are translated into Type-5 LSAs by the ASBR of Area 2 and
distributed into the OSPF AS. However, Area 1 is an NSSA area, so these Type-5 LSAs cannot travel to
Area 1.
Like stub areas, virtual links cannot transit NSSA areas.
Figure 1-4 NSSA area
Comparsion between the areas
Figure 1-5 Comparison between the areas
Figure 1-5 shows the comparison of the areas:
A totally stub area can import Type 3 default routes advertised by the ABR, while it does not import
external routes and inter-area routes.
Compared with a totally stub area, a stub area can import inter-area routes.
Compared with a stub area, an NSSA area can import external routes through Type 7 LSAs
advertised by the ASBR to the area.
Compared with an NSSA area, a totally NSSA area does not import inter-area routes.

Classification of Routers

Router types
The OSPF routers fall into four types according to the position in the AS:
1) Internal Router
All interfaces on an internal router belong to one OSPF area.
2) Area Border Router (ABR)
An area border router 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 area border router
and the backbone area can be physical or logical.
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