RPF
The golden rule: Reverse Path Forwarding (RPF)
- A router accepts a multicast packet from a source if and only if the packet has been received over the interface used to send unicast packets to the source
- If the RPF test succeeds, the packet is forwarded to all the interfaces included in the router’s OIF (Outgoing Interface List)
- If the RPF test fails, the multicast packet is discarded
- A packet should never be re-sent over the RPF interface (to avoid loops)