DMVPN Phase 1 OSPF Routing

This topic is to discuss the following lesson:

Hi Rene,

If we configure the stub area and the spoke receive the default route, the default route will not take any effect as we still have a static default route at the SPOKE router which pointing to the internet gateway. We still not able to reach to the IA route from the spoke router in this case right?

Davis

Hi Davis,

Good question and yes, this is an issue. In my example I could use default routes since the routers are directly connected. In a real network however you are probably using a default route towards the ISP.

In that case you shouldn’t use a default route but a summary route instead.

Rene

In the “Non Broadcast” configuration section ; I’m a little bit confused about the neighbor command.

With my GNS3 IOS :

* The neighbor command expects that the interface be configured as point-to-multipoint. And, finally ; it does not turn the interface to NBMA.

* The command ip ospf network non-broadcast does perfectly the job.

What exactly is the difference between the two commands ?

Hello Maodo

In order to configure the network as an NBMA, it is necessary to enter the ip ospf network non-broadcast command. If that is done, then in order to get the OSPF functioning correctly, the neighbor command must be issued. This is because when you configure the interface as an NBMA, neighbor relationships will not form automatically.

Now in @ReneMolenaar’s lesson, the command ip ospf network non-broadcast was not actually included in the lesson. It was assumed. It might be worth clarifying that in the lesson. I will let @ReneMolenaar know…

I hope this has been helpful!

Laz

For last ospf example, it seems the configuration below is missing ?
network 1.1.1.1 0.0.0.0 area 0

172.16.123.x/32 subnets are shown. It was not supposed, since Tunnel0 is configured as /24 ? 172.16.123.0/24 is already connected to the router, it was not supposed to appear as O route prefix ?

172.16.0.0/16 is variably subnetted, 4 subnets, 2 masks
O 172.16.123.1/32 [110/1000] via 172.16.123.1, 00:10:32, Tunnel0
O 172.16.123.2/32 [110/2000] via 172.16.123.1, 00:10:32, Tunnel0

Hello Maodo

In the final example where Rene shows a stub network, it is assumed that this has been configured from the previous sections. However, it may be clearer to include it here. I will let Rene know…

Laz