Troubleshooting Routes Flapping Problem in RIP

Running RIP in a complex environment can sometimes cause flapping of routes. Route flapping refers to routes coming into and going out of the routing table. To check whether the routes are indeed flapping, check the routing table and look at the age of the routes. If the ages are constantly getting reset to 00:00:00, this means that the routes are flapping. Several reasons exist for this condition. This section discusses one of the common reasons? packet loss because the packet is dropping on the sender's or receiver's interface. The example in this section considers Frame Relay because it is the most common medium in which this problem occurs. The packet loss can be verified through the interface statistics by looking at the number of packet drops and determining whether that number is constantly incrementing.

Figure 3-47 shows the network setup that can produce RIP route flapping.

Figure 3-47. Network Vulnerable to RIP Route Flapping

Figure 3-47. Network Vulnerable to RIP Route Flapping

Router 1 Router!

Figure 3-48 shows the flowchart to follow to solve this problem.

Figure 3-48. Flowchart to Solving the RIP Route Flapping Problem

Figure 3-48. Flowchart to Solving the RIP Route Flapping Problem

Debugs and Verification

In a large RIP network, especially, in a Frame Relay environment, there is a high possibility that RIP updates are lost in the Frame Relay cloud or that the RIP interface dropped the

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