Area Default cost

Area Default cost

The ABR will advertise a default route with a cost of 1. The cost of the serial link between two routers is 64. Then total cost of default route to be 64+1=65. This default cost can be changed with the command area default-cost (cost)

Router ospf 1

Network 1.1.1.0 0.0.0.255 area 21

Area 21 stub

Area 21 default-cost 20

Now the resulting cost increase route cost 64+20=84. Changing the cost of default route has no benefit here but may be useful in stub areas with more than one ABR. Normally, each internal router will chose the default route with the lowest cost. By manipulating the advertised cost, the network administrator could cause all internal routers to use the same ABR. The second ABR, advertising a higher cost, would be used only if the first were to fail.