How to configure OSPF NSSA (Not So Stubby) Area

[ali_luay_92 (Ali L)]

I want to apply Stub in one of my sites
My Design is Hub and Spokes
Each spoke in site have many routers behind it, Each Site has internet from it’s Site itself
Internet—Area 0–Area 1–Internet
If I applied Stub, My sites will not reach O E1, O E2 from Other sites because no default route my Spoke will get as long as this spoke already have default route toward ISP to reach internet
What is the best solution here?

[lagapidis (Lazarus Agapidis)]

Hello Ali

Typically, at each spoke, the default route should lead you out to the Internet. That means that you need to have something more specific than a default route that routes your traffic from one spoke to another. In the lesson, the NSSA uses a default route. That’s the beauty of the NSSA…

However, you can’t have that in your topology, because your default route leads out to the Internet. In your specific scenario, each spoke router must know the specific subnets behind all the other spoke routers in order to route traffic correctly. Stubs will not allow you to do that. I suggest that you do not configure any kind of stub network, but perform route summarization in order to reduce the size of the routing table at each spoke. It seems that each site is in a different area, so summarization between areas is possible. Take a look at the following lesson for more info…

How to configure OSPF Summarization

I hope this has been helpful!

Laz

[ali_luay_92 (Ali L)]

Which is best ospf network type for my design?
All connected through isp with same vlan.
@lagapides

[lagapidis (Lazarus Agapidis)]

Hello Ali

Take a look at this response here:

OSPF Non-Broadcast Network Type over Frame-Relay

Hello Ali First of all, having 60 OSPF routers in a single broadcast domain will cause you problems. And if I understand correctly, you have a hub and spoke topology, so all of the remote routers are listening to broadcast traffic on this single subnet over their WAN connections. So you’re using up bandwidth unnecessarily, and you are also causing the routers to look at broadcasts that do not belong to them, so they continually discard them. The best way to resolve this issue is not to choos…

I hope this has been helpful!

Laz

[Giovanni (Giovanni Cesare O)]

Hi

Why I have in a routing table a summary route without configure"area X nssa default-information-originate" ?
After configuring the command on ABR the output didnt change.

I’ve built a symple lab topology with 3 areas…A1(stub)<—(backbone)–>A2(nssa)

[lagapidis (Lazarus Agapidis)]

Hello Giovanni

@Giovanni

Why I have in a routing table a summary route without configure"area X nssa default-information-originate" ?

The area X nssa default-information-originate command does not introduce a summary route into the routing table. It should introduce a default route. Now having said that, there are various commands that may have caused a summary route to appear in your routing table. This includes commands such as area range or summary-address to name a couple.

@Giovanni

After configuring the command on ABR the output didnt change.

The area X nssa default-information-originate command when applied to an ABR should create a default route that should show up as an NSSA External Type 2 (O*N2) in the routing table of the neighbor that exists within the NSSA (as seen in the lesson). If that hasn’t happened, you should examine the rest of your configuration.

Let us know a little more about your topology and your configuration so that we can help you further.

I hope this has been helpful!

Laz