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

This topic is to discuss the following lesson:

Keep in mind that the physical interface for frame-relay is always non-broadcast.

Hi Rene!
I´ve tried the way you said but it didn´t work! So i google it and found a command
Spoke(config-if)# ip ospf network broadcast, after that it worked!

Hi Gabriel,

OSPF network broadcast will work but it’s normally used for frame-relay point-to-multipoint topologies like in this example. For frame-relay point-to-point it’s best to use the point-to-point or point-to-multipoint network type.

On the other hand, you can make all the OSPF network types work on any given topology…

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Hi Rene!
correct ur code plz!
it needs:

Spoke(config-if)# ip ospf network point-to-point
and without this,

#show ip ospf neighbor
doesnt show anything.
for example I used it in my code and just after that:

Router(config-if)#
00:26:29: %OSPF-5-ADJCHG: Process 100, Nbr 192.168.2.1 on Serial2/0 from LOADING to FULL, Loading Done

Hi Sarah,

Take a close look at the syslog message of your OSPF neighbor, you are running OSPF on the physical interface. By default OSPF configures the physical interface as “non-broadcast”. If you use a point-to-point sub-interface, OSPF will automatically configure it as the point-to-point network type :slight_smile:

Rene

ok thanks Rene, I didn’t know this.

Hey Rene! Congrats on your splendid easy-to-remember OSPF network types. My question is this: why would you wanna use any of these network types? Are there preferable ones over others? Are there any tech limitations between SP’s?

Hi Apostolis,

Nowadays you really don’t have too worry much about these network types on a real network. For a point-to-point link you can just use “point-to-point” and for Ethernet just use the “broadcast” type. The others are more for networks like frame-relay but you won’t see that much anymore…

Rene

Just get CCNA today !
Thanks René

thanks for this awesome lesson and breakdowns of network types, i understand them clearly.
Just a question, what does multipoint on subinterface do? like “int s1/0.111 multipoint” is it the same with point-to-multipoint?

Hi John,

By default the physical interface for frame-relay is always point-to-multipoint. If you only have point-to-multipoint then there’s no need to use the sub-interface.

If you have a combination of point-to-point and point-to-multipoint then you should create sub-interfaces, one for point-to-point and another for point-to-multipoint.

Rene

Hi Rene,

You mentioned that Point-to-Point Connection also Can be used for single IP subnets ? How can this happen ? I think we have overlabs with sub-interfaces ? or I’m wrong ?
Can you please explain what do you mean at this point ?

hussein sameer

Hi Hussein,

Point-to-point is used when you have one subnet per PVC, unlike point-to-multipoint where you can have one subnet for multiple PVCs.

What do you mean with the overlapping sub-interfaces? we don’t have any here :slight_smile:

Rene

Hi Rene,

At the beginning of lesson you mentioned that we have to know four things about OSPF point-to-point :-

1- Automatic neighbor discovery so no need to configure OSPF neighbors yourself.
2 - No DR/BDR election since OSPF sees the network as a collection of point-to-point links.
3 - Normally uses for point-to-point sub-interfaces with an IP subnet per link.
4 - Can also be used for single IP subnets.

I did not understand the last one ??

Hi Hussein,

I just reworded it as it sounds a bit confusing. What I meant is that you can use OSPF point-to-point as well on frame-relay topologies where you have multiple PVCs and only one subnet.

Rene

Thanks Rene I got it now

Nice article.

But is it possible to simplify examples with ethernet also ?

In a datacenter its hard to find serial interfaces.

Hi Ajith,

The reason we use frame-relay here is because it’s a CCNP ROUTE topic.

On Ethernet interfaces, it’s much simpler…the default OSPF network type is “broadcast” and there’s not really a reason to change it. If it’s an Ethernet link between two routers then you could change it to point-to-point since there’s no reason to have a DR/BDR election there.

Rene

Thanks for the reply Rene.

yeah i agree with you as OSPF topics are designed as CCNP ROUTE topic.