Ethan Banks On productivity.

OECG – Chapter 20


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
  • 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.
By Ethan Banks
Ethan Banks On productivity.

You probably know Ethan Banks because he writes & podcasts about IT. For example, he co-authored "Computer Networks Problems & Solutions" with Russ White.

This site is Ethan on productivity--not tech so much.

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