OSPF Broadcast Network Type over Frame-Relay

In a previous lesson I explained the OSPF Non-Broadcast Network Type. Now it’s time for the broadcast network type. If you understand non-broadcast then this one is easy. It’s the EXACT same thing except we don’t have to configure neighbors. OSPF will use multicast and discover OSPF neighbors automatically. The broadcast network type is the default for Ethernet interfaces.

This is the topology that we’ll use:

ospf network type topology

Hub(config)#interface serial 0/0
Hub(config-if)#ip address
Hub(config-if)#encapsulation frame-relay
Hub(config-if)#ip ospf network broadcast
Hub(config)#router ospf 1
Hub(config-router)#network area 0

Here is the configuration of the Hub router. You can see I used the ip ospf network broadcast command to change the OSPF network type. Here are the spoke routers:

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Forum Replies

  1. Hello Sims!

    The network topology that you are describing would not COMPLETELY simulate the frame relay situation in this lesson. What you are describing would require all communication between R1 and R3 to go through R2 just like in the lesson, however, this also means that the two interfaces on R2 that connect R1 and R3 would have to be on the same subnet, something that is not possible. So you would just be creating two point to point links on different subnets, however, in the frame relay example in the lesson, all three routers are in the same subnet.


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  2. Hello Sims!

    Although I’m sure you know most of this, let me start by stating the network types for OSPF and stating an example for each:

    **Point to Point** - a serial connection between two routers
    **Broadcast** - two or more routers on the same subnet connected to an Ethernet switch

    The next two types of network are used to accommodate multi access technologies that don’t support broadcast. These technologies include Frame Relay and ATM.

    **Non Broadcast Multi Access** - This is used when you have multiple routers connected on the same subnet over a non-broadc

    ... Continue reading in our forum

  3. Hello Laz,

    Thank you so much for your guidance, this absolutely cleared my doubt.


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