If an exported route was learned from a member of the same RIP group, the metric associated with that route is the normal RIP metric. For example, a RIP route with a metric of 5 learned from a neighbor configured with an incoming metric of 2 is advertised with a combined metric of 7 when advertised to neighbors in the same group. However, if this route was learned from a RIP neighbor in a different group or from a different protocol, the route is advertised with the metric value configured in the outgoing metric for that group. Figure 71 shows a network with alternate routes between Routers A and D.
Figure 71: Controlling Traffic in a RIP Network with the Outgoing Metric
In this example, each route from Router A to Router D has two hops. However, because the link from Router A to Router B in RIP group Beta 1 has a higher bandwidth than the link from Router A to Router C in RIP group Alpha 1, you want traffic from Router D to Router A to flow through Router B. To control the way Router D sends traffic to Router A, you can alter the routes that Router D receives by configuring the outgoing metric on Router A's interfaces in the Alpha 1 RIP group.
If the outgoing metric for the Alpha 1 RIP group—the A-to-C link—is changed to 3, Router D calculates the total path metric from to A through C as 4. In contrast, the unchanged default total path metric to A through B in the Beta 1 RIP group is 2. The fact that Router A's interfaces belong to two different RIP groups allows you to configure two different outgoing metrics on its interfaces, because you configure path metrics at the group level.
By configuring the incoming metric, you control the way Router A sends traffic to Router D. By configuring the outgoing metric on the same router, you control the way Router D sends traffic to Router A.
To modify the outgoing metric on Router A and force traffic through Router B:
Table 122: Modifying the Outgoing Metric