OSPF Point-to-Multipoint Network Type over Frame-Relay

(Rene Molenaar) #1

This topic is to discuss the following lesson:

(Apoorva J) #2

Hey,

Since we are using a frame relay network and I see that you have not included a broadcast command with the the frame relay command, how do the OSPF neighbors identify each other? As mentioned before without the broadcast command no multicast traffic will pass. Is this behavior because of point to point topology? How will the Hub/Spoke know that it has an OSPF speaking router on the other end, if no multicast traffic is flowing?

(Lazaros Agapides) #3

Hello Apoorva

RFC 2328 indicates what kind of hello and LSA communication OSPF uses for each type of network. These are summarized below:

  • Point-to-Point (P2P) - Multicast
  • Point-to-Multipoint (P2MP) - Unicast
  • Broadcast - Multicast
  • Non-broadcast multiple access (NBMA) - Unicast
  • Virtual Link - Unicast

This means that the Point to Multipoint communication between OSPF routers is unicast.

Now having said that, when you configure the frame relay maps in your configuration, you will require the broadcast keyword. The frame relay maps are not actually shown in the lesson so this is why you don’t see the broadcast keyword anywhere.

I hope this has been helpful!

Laz