212 Words. Plan about 1 minute(s) to read this.
The book spends all of a single page discussing the 2 multicast routing protocols DVMRP & MOSPF. So I won’t belabor them beyond these notes in the book
Distance Vector Multicast Routing Protocol (DVMRP) – RFC 1075
- IOS doesn’t support full-blown DVMRP, although you can hook up an IOS router to a DVMRP network.
- DVMRP uses a distance vector routing protocol similar to RIPv2. Routes get sent every 60 seconds. 32 hops is infinity.
- DVMRP uses Probe messages (not Hellos like PIM) to find neighbors via 184.108.40.206.
- DVMRP uses a “truncated broadcast tree”, like an SPT, but with some of the links pruned (unlike PIM-DM, where the router forwards the multicast to all attached segments unless a prune has happened.)
Multicast Open Shortest Path First (MOSPF) – RFC 1584
- An extention to OSPFv2 unicast routing.
- MOSPF uses a group membership LSA, type 6.
- The SPT is calculated on-demand, when a multicast for a group first shows up.
- All OSPF routers will know where all the multicast group members are, because of the type 6 LSAs.
- All OSPF routers will have multicast routes based on the SPF calculation.
- RPF checking is not needed, since OSPF performs the Dijkstra calculation and know who’s upstream and who’s downstream.
- MOSPF requires OSPF to be running – they are interdependent.
- IOS does not support MOSPF.
Ethan Banks writes & podcasts about IT, new media, and personal tech.
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