Summary

This chapter presented you with methods for troubleshooting common PIM problems. The section on troubleshooting PIM dense mode presented a case study of RPF check failure. Most problems in PIM stem from the RPF check failure problem. Troubleshooting an RPF failure problem requires an up-to-date network diagram, as well as some scrutiny of the unicast and multicast routing tables. If necessary, turning on multicast debugging will provide some clues to solving the problem. When troubleshooting a multicast problem, the show ip mroute command is the main troubleshooting tool. In many cases, the network administrator needs to go hop by hop through the multicast trees and look at the multicast routing table at each hop to correctly determine the cause of the multicast problem.