12.7.1 Overview
If the connection with neighboring router is incomplete or unstable, the entire routing might become unstable. This situation might occur when starting, restarting or adding a router to the network. In such a situation, the OSPF protocol allows a router to disseminate routing information that persuades nearby devices to use alternate routes. A router that uses this behavior is called a stub router in OSPF. This functionality allows you to prevent instability in a specific device from destabilizing the rest of the network.
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(1) Max metric
A stub router advertises the maximum cost of 65535 for all of its connected OSPF interfaces. This action gives OSPF routes through the stub router a higher cost than their alternatives.
However, if the interface is a stub network (having no neighboring routers), the stub router will advertise the cost specified in the configuration. The routes advertised by the stub router might take priority over the stub network or external AS routes.
The maximum metric advertised for routes through the stub router causes nearby routers to give priority to alternate routes. You can also use the address of the stub router for Telnet or SNMP management or to exchange BGP4 routing information.