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

In a previous lesson I showed you how to configure the OSPF point-to-multipoint network type. This time we’ll look at the OSPF point-to-multipoint non-broadcast network type. It’s the exact same thing but we’ll have to specify OSPF neighbors ourselves. Here is the topology that we’ll use:

OSPF Network Type Topology

There are a couple of things that you need to be aware of:

  • No Automatic neighbor discovery so you need to configure OSPF neighbors yourself!
  • No DR/BDR election since OSPF sees the network as a collection of point-to-point links.
  • Only a single IP subnet is used in the topology above.

Here’s the configuration for the Hub router:

Hub(config)#interface serial 0/0
Hub(config-if)#ip address 192.168.123.1 255.255.255.0
Hub(config-if)#encapsulation frame-relay
Hub(config-if)#ip ospf network point-to-multipoint non-broadcast
Hub(config-if)#exit
Hub(config)#router ospf 1
Hub(config-router)#network 192.168.123.0 0.0.0.255 area 0
Hub(config-router)#neighbor 192.168.123.2
Hub(config-router)#neighbor 192.168.123.3

This is the hub configuration. I changed the network type to point-to-multipoint non-broadcast, advertised the 192.168.123.0 /24 network in OSPF and most important…specified the OSPF neighbors myself. Let’s look at the spoke router configuration:

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Forum Replies

  1. Hi Lee,

    I don’t have a rhyme but there’s some logic to these OSPF network types:

    Only broadcast and non-broadcast require a DR/BDR election since OSPF sees these network types as “multi-access”. Everything with “point” in it is seen as a collection of point-to-point links so there is no DR/BDR election.

    Everything with “non-broadcast” requires you to configure neighbors since OSPF won’t be able to find them by itself.

    Only with point-to-point we use a subnet for each PVC, all other OSPF network types usually have a single IP subnet.

    Still some memorization to d

    ... Continue reading in our forum

  2. Hi, Rene

    I hope you are doing great.

    I have one question:

    - why are you using the command network in order to auto discover the neighbors If you are statically defining them with the command neighbors ?

    Have a great day.

  3. Hi John,

    Glad to hear you like it. OSPF will change its timers based on its OSPF network type :slight_smile:

    Rene

  4. Hi Rene,

    Nice article.

    But OSPF network types are still a confusing topic after going through your articles. Is it possible to simplify things with a single post where you can update the differences and purpose of different network types. ?

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