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and RouterF. If you do not change the default metric configuration, RIP traffic can<br />

go along either path. You can check the path it has chosen at this moment, which is<br />

the path through RouterB:<br />

aviva@RouterA> traceroute 192.168.24.1<br />

traceroute to 192.168.24.1 (192.168.24.1), 30 hops max, 40 byte packets<br />

1 10.0.21.2 (10.0.21.2) 23.712 ms 29.928 ms 31.495 ms<br />

2 10.0.22.2 (10.0.22.2) 49.921 ms 68.857 ms 100.153 ms<br />

3 192.168.24.1 (192.168.24.1) 100.107 ms 100.417 ms 99.953 ms<br />

To control the path selected between RouterA and RouterD, you set the inbound<br />

metric on RouterA’s serial interface to 2. Whenever RouterA receives a route on the<br />

se-0/0/3 interface, it sets the metric in that route to 2:<br />

aviva@RouterA> show rip neighbor<br />

Source Destination Send Receive In<br />

Neighbor State Address Address Mode Mode Met<br />

-------- ----- ------- ----------- ---- ------- ---<br />

fe-0/0/1.0 Up 10.0.15.2 224.0.0.9 mcast both 1<br />

se-0/0/3.0 Up 10.0.21.1 224.0.0.9 mcast both 2<br />

You use the traceroute command again to see that you are forcing traffic through<br />

RouterE:<br />

aviva@RouterA> traceroute 192.168.24.1<br />

traceroute to 192.168.24.1 (192.168.24.1), 30 hops max, 40 byte packets<br />

1 10.0.15.1 (10.0.15.1) 20.245 ms 11.334 ms 17.559 ms<br />

2 10.0.13.2 (10.0.13.2) 19.916 ms 19.534 ms 18.065 ms<br />

3 192.168.24.1 (192.168.24.1) 21.769 ms 29.599 ms 19.960 ms<br />

You check the routing table to see that the route to RouterD through RouterBhas a<br />

metric of 4, while the route through RouterE has a metric of 3:<br />

aviva@RouterA> show route table inet.0<br />

10.0.29.0/24 *[RIP/100] 00:16:27, metric 4, tag 0<br />

to 10.0.15.1 via fe-0/0/1.0<br />

> to 10.0.21.2 via se-0/0/3.0<br />

10.0.31.0/24 *[RIP/100] 02:56:55, metric 3, tag 0<br />

> to 10.0.15.1 via fe-0/0/1.0<br />

Changing the inbound metric on a router’s interface modifies only how the local<br />

router, RouterA, sends traffic. It has no effect on how any remote routers control<br />

their traffic flow. You can look in the routing table of RouterD to see that when it<br />

sends traffic to RouterA, the two paths (through RouterC and RouterF) both have a<br />

metric value of 3, which is the value you expect because RouterA is three hops away<br />

from RouterD:<br />

aviva@RouterD> show route table inet.0<br />

10.0.15.0/24 *[RIP/100] 03:39:30, metric 3, tag 0<br />

> to 10.0.31.2 via t1-0/0/2.0<br />

10.0.21.0/24 *[RIP/100] 03:41:18, metric 3, tag 0<br />

> to 10.0.29.1 via fe-0/0/1.0<br />

344 | Chapter 10: RIP<br />

This is the Title of the Book, eMatter Edition<br />

Copyright © 2008 O’Reilly & Associates, Inc. All rights reserved.

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