GRE tunnels are useful in many ways. This blog post shows how to set up multicast routing with pimd over a GRE tunnel. To achieve this we will also set up OSPF over GRE with Quagga, because PIM, unlike DVMRP (mrouted), require unicast routing rules to be established. .----{ Intranet }----. / 192.168.1.0/24 \ / \ .10 / \.20 .--'---. .1 GRE Tunnel .2 .---`--. | |====================| | | R1 | 172.16.16.0/30 | R2 | | | | | '--.---' '------' | .1 | .1 | 10.0.1.0/24 | 10.0.2.0/24 | .2 | .2 .--'---...
