Configuring gated

Configuring the OSPF Protocol

Figure 3-3

Areas Defined in an Autonomous System

Area 1

 

C

D

Other AS

1

 

A

B

E

 

 

2

3

 

 

Legend:

 

 

 

 

 

 

 

Network

F

 

 

I

Router

Area 2

 

Area 3

 

Area

 

 

 

4

G

5

H

Backbone

6

Internal routers have all their directly connected networks in the same area. In Figure 3-3, routers A, B, and H are internal routers.

Routers that are connected to multiple areas are called area border routers. In Figure 3-3, routers F and G are area border routers.

Routers that connect one AS to another are called AS boundary routers. In Figure 3-3, router D is an AS boundary router.

Neighbor routers are routers that interface to a common network. OSPF uses its own Hello subprotocol to determine which routers are neighbors. In Figure 3-3, routers A, B, and C are a set of neighbor routers that interface to network 1, while routers A and F are another set of neighbor routers that interface to network 2.

NOTE

The Hello subprotocol used with OSPF is not the same as the gated

 

HELLO protocol. The Hello subprotocol is still supported.

 

 

Chapter 3

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