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| 5.4 |  | Troubleshooting RIP |
| 5.4.3 |  | Reaches RIP hop count limit |

The RIP metric maximum is 15 hops. If a network has more than 15 hops, RIP is not a suitable protocol. Figure shows a network that produces a RIP hop-count limit problem. Router R2 is receiving an update for a RIP route, which is more than 15 hops away. R2 does not install that route in the routing table, as demonstrated in the output.

Debugs and Verification
The most logical way to start troubleshooting this problem is to look at the routing table of the intermediary routers along the way (R1 in this example) and determine whether they are receiving a route for the 131.108.6.0/24 network. Figure shows that router R1 is receiving RIP routes for the 131.108.6.0/24 network.

Router R1 is receiving the route in question, but with a metric of 15. R1 will add 1 more to 15 when it advertises this route to R2, which results in an infinite metric, consequently preventing the route from being placed in the routing table.

To verify this, use the output of debug ip rip command on R1. The RIP update for the 131.108.6.0/24 network is being sent with a metric of 16 out its Ethernet 1 interface towards router R2.

Figure shows the output of debug ip rip command on router R2. Router R2 receives this update and discards it because the metric shows that this network has an infinite distance and is therefore unreachable.

Solution
This is a classical RIP problem in which a route passes through more than 15 devices. IP networks these days usually have more than 15 routers. There is no way to overcome this behavior other than to use a routing protocol that does not have a 15-hop limitation. IGP routing protocols that do not have this limitation include OSPF, IGRP, EIGRP, and IS-IS.