Installing and Administering Internet Services

354 Chapter8
Configuring gated
Configuring the OSPF Protocol
Summary link advertisements (routes to destinations outside the area
but within the AS) continue to be sent into the stub area.
The stub statement specifies that the area is a stub area. A cost clause
can optionally be defined that specifies the cost associated with the
default route to be advertised in the stub area.
Figure 8-9 shows an example of an area border router that is connected
to area 0.0.0.2 through interface 193.2.1.20. Since all traffic in and out of
area 0.0.0.2 must pass through router A, it is not necessary for the area’s
internal routers, such as router B, to receive inter-area routing
information.
Figure 8-9 Area Border Router Configuration Example
The following is an example of the stub area definition in the router’s
/etc/gated.conf file:
OSPF yes {
area 0.0.0.2 {
stub cost 5 ;
networks {
193.2.1.16 mask 0xfffffff0 ;
} ;
interface 193.2.1.20 nonbroadcast cost 5 {
enable ;
routers {
193.2.1.17 eligible ;
} ;
priority 5 ;
hellointerval 5 ;
Router
193.2.1.20
193.2.1.16 mask 0xfffffff0
193.2.1.17
193.2.1.18
193.2.1.19
Area 0.0.0.2Area 0.0.0.1
Router
B
A