Example: Controlling Traffic with an Incoming Metric

This example shows how to control traffic with an incoming metric.

Requirements
Overview
Configuration
Verification

Requirements

Before you begin, define RIP groups, and add interfaces to the groups. Then configure a routing policy to export directly connected routes and routes learned through the RIP routing exchanges. See About Disabling Integrated Convergence Services SRX Series Media Gateway Registration.

Overview

In this example, routes to Router D are received by Router A across both of its RIP-enabled interfaces as shown in Figure 1. Because the route through Router B and the route through Router C have the same number of hops, both routes are imported into the forwarding table. However, because the T3 link from Router B to Router D has a higher bandwidth than the T1 link from Router C to Router D, you want traffic to flow from A through B to D.

Figure 12: Controlling Traffic in a RIP Network with the Incoming Metric

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To force this flow, you can modify the route metrics as they are imported into Router A's routing table. By setting the incoming metric on the interface from Router A to Router C, you modify the metric on all routes received through that interface. Setting the incoming route metric on Router A changes only the routes in Router A's routing table, and affects only how Router A sends traffic to Router D. Router D's route selection is based on its own routing table, which, by default, includes no adjusted metric values.

In the example, Router C receives a route advertisement from Router D and readvertises the route to Router A. When Router A receives the route, it applies the incoming metric on the interface. Instead of incrementing the metric by 1 (the default), Router A increments it by 3 (the configured incoming metric), giving the route from Router A to Router D through Router C a total path metric of 4. Because the route through Router B has a metric of 2, it becomes the preferred route for all traffic from Router A to Router D.

This example uses a RIP group called alpha 1 on interface g3–0/0/0.

Configuration

Step-by-Step Procedure

To control traffic with an incoming metric:

Create an interface.
[edit]user@host# edit protocols rip group alpha1 neighbor ge-0/0/0
Set the incoming metric.
[edit]user@host# set metric-in 3
If you are done configuring the device, commit the configuration.
[edit]user@host# commit

Verification

To verify the configuration is working properly, enter the show protocols rip command.