Useful Multicast Addresses

Whilst multicast has been removed from the new CCNPv6 exams this still doesn’t mean you get to escape it, there are several addresses that I sometimes find hard to remember which is which which are detailed below.

A lot of the modern routing protocols (RIPv2, EIGRP, OSPF) use multicast over the older method of broadcast (RIPv1) to communicate with adjacent routers/neighbours. This gives the advantage that not all hosts will receive and therefore have to process these packets that are for instance destined for the EIGRP process as they do not subscribe to the relevant multicast address.

224.0.0.1 – The All Hosts multicast group that contains all systems on the same network segment. 224.0.0.2 – The All Routers multicast group that contains all routers on the same network segment. 224.0.0.5 – The OSPF All Routers address. Used to send Hello packets to all OSPF routers on a network segment. 224.0.0.6 – The OSPF All DR Routers address. Used to send OSPF routing information to OSPF designated routers on a network segment. 224.0.0.9 – The RIP version 2 group address. Used to send routing information using the RIP protocol to all RIP v2-aware routers on a network segment. 224.0.0.10 – EIGRP group address. Used to send EIGRP routing information to all EIGRP routers on a network segment.