Preventing routing updates through an interface

Preventing routing updates through an interface

7.2.7 This page will teach students how to prevent routing updates.

Route filtering regulates the routes that are entered into or advertised out of a route table. These have different effects on link-state routing protocols than they do on distance vector protocols. A router that runs a distance vector protocol advertises routes based on what is in its route table. As a result, a route filter influences which routes the router advertises to its neighbors.

Routers that run link-state protocols determine routes based on information in the link-state database, rather than the route entries advertised by neighbor routers. Route filters have no effect on link-state advertisements or the link-state database. For this reason, the information on this page only applies to distance vector IP routing protocols such as RIP and IGRP.

The passive-interface command prevents the transmission of routing updates through a router interface. When update messages are not sent through a router interface, other systems on the network cannot learn about routes dynamically. In Figure , Router E uses the passive-interface command to prevent routing updates from being sent.

For RIP and IGRP, the passive-interface command stops the router from sending updates to a particular neighbor, but the router continues to listen and use routing updates from that neighbor.

The Lab Activities will instruct students on how to prevent routing updates through an interface.

The next page will explain the concept of load balancing.

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