OSPF Broadcast Network Type over Frame-Relay

Lessons Discussion
1

This topic is to discuss the following lesson:

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Thanks René! This explanation was so clear!

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Hi René…excellent job, thanks for your help!!!

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Hey Rene. My understanding is that broadcast is the default network type for ethernet interfaces and nonbroadcast is the default for serial interfaces. In the lesson you stated that the ip ospf broadcast command is not necessary in this example, but wouldn’t it be required since you’re configuring it on a serial interface?

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Hi Thomas,

I just fixed it, you are correct. Broadcast is the default for Ethernet and non-broadcast for serial interfaces. The only exception is when you create a point-to-point sub-interface for frame-relay, the default will be point-to-point.

Rene

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Rene… If we do not mention the OSPF network type then by default what network type OSPF gonna pick? By default it would be Broadcast Multi access or P2P not multiaccess?

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Hi Adil,

It depends on the interface type, on Ethernet interfaces OSPF will pick broadcast as default. On PPP serial interfaces it will select point-to-point.

Rene

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9

A post was merged into an existing topic: OSPF LSA Types Explained

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Hi,
Why don’t you remove frame relay since cisco also removed from their subject
Thanks

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Hello Sims

Actually, Frame relay may not be an official topic in the curriculum, however, OSPF network types are. So in order to be able to describe the various network types that OSPF can be configured with, it’s necessary to use a technology that is non broadcast to show how to configure it.

I hope this has been helpful!

Laz

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12

Hi,
is it possible without frame relay . so the labbing will be easy
Thanks

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13

Hello Sims

In order to be able to employ the various types of OSPF networks, you need to employ technologies that are “non broadcast” “point to point”, and “point to multipoint”. Ethernet is a broadcast multiaccess technology and thus will not do for configuring OSPF with these features. The only technology that can be readily labbed up that can be used with these OSPF features is Frame Relay.

I hope this has been helpful!

Laz

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Hi Laz,

Can these technologies be employed over DMVPN?

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Hello Joseph

You can indeed employ OSPF over DMVPN, and you are able to apply any of these OSPF network types to the topology. There are various advantages and disadvantages for each. Remember that DMVPN has three configuration types called Phases. For each of these Phases, some OSPF network types are applicable some are not. The following three lessons show the various OSPF network types you can use for each DMVPN Phase configuration:




I hope this has been helpful!

Laz

1 Like
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Hello everyone,
René, I have a doubt about frame-relay technology. The impediment to the transmission of traffic in broadcast is due to the technology itself or because of ospf.

I ask this because in this lesson we saw two networks based on FR, but one supporting broadcast and the other not.

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Hello Neves

Frame relay as a technology does not support broadcasts. It is not considered a multi-access technology like Ethernet where you can have more than two hosts on a network segment. Network segments for Frame-relay consist of a single point to point connection with two hosts, one on each end. Now this point-to-point arrangement can be seen in the way the DLCIs are used. You have one DLCI for each circut, and you have a device on each end of that circuit.

Now if you were to implement a routing protocol like OSPF on a Frame-relay network, which requires broadcast to function, then you must simulate broadcast functionality. You can find out how to do this in the following lesson:

I hope this has been helpful!

Laz

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18

Thanks, its was helpfull.

1 Like
19

Hi
I hope i can get fast response
Now in these days we don’t use FR, What is the most network types used in real life and which is the best for Hub and Spoke design connected through isp with same broadcast domain?

Also I need use cases for OSPF Network type without FR, As long as FR will not be used.

@ReneMolenaar @lagapidis

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Hello Ali

The OSPF network type you use should be appropriate for the network topology in question. Yes, frame-relay is not something used very much any longer, but there are other network topologies that may use a network type other than the broadcast network type which is the default for Ethernet interfaces.

DMVPN is a prime example of a topology that can use different network types. You can see examples of how they are used in the following lessons:

I assume your question here has to do with the hub and spoke topology you mention in another one of your posts. You can see the response to that post here:

I hope this has been helpful!

Laz

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since we use broadcst ospf, frame relay is configured with broadcast, why i do not get neighborship with r2,r3 (same fr relay topolgy as lesson ) ?