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

Hi Rene,

So with those types of network types ( so far 5 ) , is there any preference to use one over the other for frame relay and why ?

thx

Ahmad

Hi Ahmad,

They all work so it doesn’t matter too much which one you pick.

The point-to-point or point-to-multipoint network types are probably the easiest to use. You don’t require a DR/BDR election so you don’t have to worry about setting the correct priority.

Rene

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19 posts were merged into an existing topic: OSPF Point-to-Point Network Type over Frame-Relay

I have a customer that is designing 4 areas in a ring configuration using /30s to Area 0 /24 DR and asked if he could make the 4 area rings network point to point connections between each router. Is this a good design? I told them it should be OK as long as a DR/BDR lived in Area 0.

Thoughts

Mike C.

Hello Michael.

I refer to yout @ReneMolenaar’s previous post where he states that [quote=“ReneMolenaar, post:24, topic:921”]
They all work so it doesn’t matter too much which [network topology] you pick.

The point-to-point or point-to-multipoint network types are probably the easiest to use. You don’t require a DR/BDR election so you don’t have to worry about setting the correct priority.
[/quote]

So it really doesn’t matter which network type you choose, as long as they are configured correctly.

However, keep the following issues in mind:

* If each area is composed of a point to point connection between routers, you do not require DR/BDRs at all.
* Secondly if you are creating four areas and these areas connect to each other in a ring topology, then one of these areas will not be directly connected to area 0. You will require either a virtual link (which is not advisable as a permanent solution) or you will need to revise the topology.

I hope this has been helpful!

Laz

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Hi Rene,
Why there is no Point-To-Point non-broadcast type, I mean by the Design of OSPF why there is no such type ??
Kind Regards,
Hussein Samer

Hi Hussein,

There’s no need to, at the other end of a point-to-point connection there is only 1 other device…

Broadcast traffic can be used on multi-access network, like Ethernet where you want everyone to receive certain traffic.

Rene

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Hi Guys,

Why is it that for Point-to-Multipoint (Broadcast or Non-Broadcast), you used the ip ospf network point-to-multipoint command and ip ospf network point-to-multipoint non-broadcast command.

But for Point-to-Point you didn’t use the “ip ospf network point-to-point”?

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Hello Joseph

Looking over the lessons, I see that for the OSPF Point-to-Point Network Type over Frame-Relay lesson, you’ll see that the configuration parameters for a serial subinterface when configuring point to point frame relay requires you to specify the type of subinterface. In this lesson, Rene is configuring the following on the Hub:

Hub(config)#interface serial 0/0.102 point-to-point

and

Hub(config)#interface serial 0/0.103 point-to-point

Notice the point-to-point keyword. When OSPF is applied to this interface, the default network type is automatically detected as point-to-point. This is specified in the OSPF command reference below:


…where it states that the default depends on the configured “network type”. So in the configuration, the ip ospf network point-to-point command could have been implemented, but was the default, so it was not necessary.

I hope this has been helpful!

Laz

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Isnt there a error in the network diagram and the command line?

192.168.123 subnet used for DLCI 103 part in network diagram but in configuration 192.168.13 subnet used

Hub(config)#interface serial 0/0.103 point-to-point
Hub(config-subif)#ip address 192.168.13.1 255.255.255.0

Hello Anoop

Yes there seem to be some discrepancies in the diagram, the IP address, as well as in the routing table at the end of the lesson.

I’ll let Rene know to fix these.

Thanks for pointing that out!

Laz

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Hi Rene,

I have a question about what kind of ospf network to configure, it all depends on who you ask, of course. Here goes!

In my company, for p2p links over ethernet the type of OSPF network I configure is ip ospf network point-to-point, since I consider that it is not necessary to have a choice of DR/BDR, regardless of whether the protocol/connection technology is Ethernet, FR, ppp, etc…

Would this be correct?

Regards.

Hello Gerard

If you have two directly connected routers over an Ethernet link and you know you won’t be adding another router to that particular network segment, then yes, it would be correct to set up the link as a point-to-point network for OSPF. The result would be that there would be no DR/BDR elections on that particular network segment.

Technically speaking, this can be achieved. The question, however, is, why would you do it? The DR/BDR election is not particularly resource-intensive, regardless of how many routes are advertised on your OSPF network. Nor is it particularly time-consuming to affect convergence time in any substantial way. Unless you have a central OSPF router with dozens or even hundreds of point-to-point Ethernet links to other OSPF routers, making such links point-to-point for OSPF will have little to no substantial benefit. By no means is it incorrect, in fact, it is theoretically more efficient.

The question however remains, is the change worth the marginal benefit? It’s really up to you. And remember, if in the future you (or your successor) happen to add another router to that particular network segment (by adding a switch for example), you will have to remember to remove that particular command from both of the OSPF routers, which is an additional point of failure in the process.

So yes you are right, it really depends on who you ask, and how each individual evaluates the benefits and drawbacks of each choice.

I hope this has been helpful!

Laz

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hello Mr Rene, already thank you for the explanation of the course, please for what purpose we will be called to configure these different types of OSPF Networks and for each Type please give me its deployment context. I hope my question is understood. thanks in advance

Hello Charles

Take a look at this NetworkLessons note on OSPF Network Types. There you will find details about each network type, including where and how it can be used. If you have any further more specific questions, feel free to let us know!

I hope this has been helpful!

Laz

A post was merged into an existing topic: THE Updated CCIE V1.1