Distance Vector Multicast Routing Protocol (DVMRP) is a widely deployed multicast routing protocol. When used with other multicast routing protocols such as Protocol Independent Multicast-Sparse Mode (PIM-SM), however, reverse path forwarding (RPF) checking can fail. RPF is a validation check to determine whether a multicast packet came from the expected path, i.e., the reverse path. A RPF check can fail because the source can be an external source, i.e., a source located outside the DVMRP domain. For example, the external source can be in a PIM multicast routing domain.
The multicast routing information table maintained in a DVMRP router is generally limited to DVMRP-generated routing information. Typically there is no mechanism for the router to get the reverse path information of a source that is outside the DVMRP domain. Consequently, multicast traffic provided to a DVMRP multicast border router (MBR) from an external source and subsequently delivered to a DVMRP router that is not a MBR generally does not include the RPF information for the external source. As a result, the multicast traffic may be dropped.
What is needed is a method to enable a non-MBR DVMRP in a DVMRP domain to perform the RPF validation check. The present invention satisfies this need and provides additional advantages.