SMC Networks SMC6724L3 manual 192, Configuring Ospf Areas, Single route. The backbone or any

default external route

CONFIGURING THE SWITCH

Configuring OSPF Areas

An autonomous system must be configured with a backbone area, designated by area identifier 0.0.0.0. By default, all other areas are created as normal transit areas.

Routers in a normal area may import or export routing information about individual nodes. To reduce the amount of routing traffic flooded onto the network, you can configure an area to export a single summarized route that covers a broad range of network addresses within the area

(page 3-196). To further reduce the amount of routes passed between areas, you can configure an area as a stub or a not-so-stubby area (NSSA).

Normal Area – A large OSPF domain should be broken up into several areas to

increase network stability and reduce the

area

ABR

amount of routing traffic required

through the use of route summaries that backbone aggregate a range of addresses into a

ABR

single route. The backbone or any

area

normal area can pass traffic between other areas, and are therefore known as

transit areas. Each router in an area has identical routing tables. These tables may include area links, summarized links, or external links that depict the topology of the autonomous system.

Stub – A stub does not accept external routing information. Instead, an area border router adjacent to a stub can be

configured to send a default external backbone ABR stub

route into the stub for all destinations outside the local area or the autonomous system. This route will also be

advertised as a single entry point for traffic entering the stub. Using a stub can significantly reduce the amount of topology data that has to be exchanged over the network.

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