Chapter 2 Advanced Routing for FortiOS 5.0 : Routing Information Protocol (RIP) : Troubleshooting RIP : Routing Loops : Action to take on discovering a routing loop
  
Action to take on discovering a routing loop
Once you have mapped the problem on your network, and determined it is in fact a routing loop there are a number of steps to take in correcting it.
1. Get any offline routers back online. This may be a simple reboot, or you may have to replace hardware. Often this first step will restore your network to its normal operation, once the routing tables finish being updated.
2. Change your routing configuration on the edges of the outage. Even if step 1 brought your network back online, you should consider making changes to improve your network before the next outage occurs. These changes can include configuring features like holddowns and triggers for updates, split horizon, and poison reverse updates.