DMVPN Phase 1 RIP Routing

Hi Rene,

I meant network 192.168.123.x

The routers are directly connected on the 192.168.123.0/24 subnet. The tunnel interfaces are sourced from this subnet.

That’s all we need for DMVPN, connectivity between the NBMA addresses so that we can establish the tunnels.

Hello Jeremy.
What version of ios images did you use? I can find the command SHOW DMVPN on the router i’m using
Thanks.

Hi Rene,

i think there is mismatch between the DMVPN PHASE 1 RIP to the results of show ip route rip command ON THE spokes routers and other DMVPN PHASE 1 PROTOCOL LETS SAY EIGRP and show ip route eigrp (look at the next hop address)

@Manhamane most labs are built using VIRL. Currently, the IOS version is 15.6.2.T

If you happen to be a GNS3 user, my favorite DMVPN image (which has everything you need) is c7200-adventerprisek9-mz.152-4.M6

@Dionisis Which output do you refer to?

Both RIP and EIGRP use the same next hop IP address in DMVPN phase 1?

Spoke1#show ip route rip 

      1.0.0.0/32 is subnetted, 1 subnets
R        1.1.1.1 [120/1] via 172.16.123.1, 00:00:17, Tunnel0
Spoke1#show ip route eigrp 

      1.0.0.0/32 is subnetted, 1 subnets
D        1.1.1.1 [90/27008000] via 172.16.123.1, 00:01:27, Tunnel0

Rene

Spoke2#show ip route rip 

      1.0.0.0/32 is subnetted, 1 subnets
R        1.1.1.1 [120/1] via 172.16.123.1, 00:00:01, Tunnel0
      2.0.0.0/32 is subnetted, 1 subnets
R        2.2.2.2 [120/2] via 172.16.123.2, 00:00:01, Tunnel0
Spoke2#show ip route eigrp | include 2.2.2.2
D        2.2.2.2 [90/28288000] via 172.16.123.1, 00:00:41, Tunnel0

but i think the sentence below explains what it happens
EIGRP changes the next hop IP address when it advertises networks.

Hi Dionisis,

That’s right, EIGRP changes it.

Rene

Hi

please check the attached clip, here ‘no ip split-horison’ or jest ‘ip split-horison’.?

Hi Noorudheen,

I don’t see an attachment but the command is no ip split-horizon.

Rene

Hi Rene,
So we call DMVPN is Dynamic mGRE alternatively , rignt ??

One more confusion regarding the output …

Spoke1#show ip route rip 

      1.0.0.0/32 is subnetted, 1 subnets
R        1.1.1.1 [120/1] via 172.16.123.1, 00:00:10, Tunnel0
      3.0.0.0/32 is subnetted, 1 subnets
R        3.3.3.3 [120/2] via 172.16.123.3, 00:00:10, Tunnel0

when Spoke1 want to reach Spoke2(3.3.3.3) , what will be next hop in DMVPN Phase 1 ?? . Its showing 172.16.123.3 but all traffic will go through HUB, right ?Thanks

br//
zaman

Hi Zaman,

mGRE (multipoint GRE) is one piece of the DMVPN puzzle. You also need NHRP.

In DMVPN phase 1, all traffic will go through the hub yes, there is no direct spoke-to-spoke communication.

Rene

Hi,

In one of last capture images, the lesson says : “Above you can see the NBMA addresses”. That is said about loopback adresses 2.2.2.2 and 3.3.3.3 that are attached to Spoke-1 and Spoke-2 routers.

In the context of NHRP, could we say that NBMA does mean the same thing as the whole underlay network (including all “public” networks learned by the Spoke) ?

Hello Maodo

The NBMA in this particular example refers to the nature of the actual physical network, and the addressing of the physical interfaces connected to the medium. That is, the 192.168.123.X subnet. So if this is what you mean by the whole underlay network, then yes you are correct.

I hope this has been helpful!

Laz

I found the definition below of NMBA :

Multi-access means we have to select a DR and BDR.
Non-broadcast means that OSPF expects us to configure neighbors ourselves.

In the article :

According to that ; it seems that NBMA is that “kind-of Frame-Relay network” DMVPN builds on the underlay Network.

Hello Maodo.

Yes you are correct.

Laz

I realised at least on my lab that using the command “ip summary address rip 0.0.0.0 0.0.0.0” does not inject a default route on the spokes, you also have to include the command “default-information originate” under the “router rip” for this to take effect.

Hello Tariq

It seems that others are having similar issues with the ip summary address command when using the RIP protocol. Even so, the solution is not the default-information originate command.

These two commands do different things.

Default-information originate will advertise default route, while ip summary-address rip 0.0.0.0 0.0.0.0 will advertise only default route and will hide topology details. Remember that the ip summary-address command can use a more specific route, such as ip summary-address rip 10.2.0.0 255.255.0.0, it does not have to be 0.0.0.0 0.0.0.0.

Others have had similar problems, and when they change the routing protocol from RIP to EIGRP, it seems that the config works. My suspicion is that you may be using RIP v1 instead of v2. Can you verify that you are indeed using v2?

Then we can take a look at other issues that may be causing this.

I hope this has been helpful!

Laz

Hello Laz,

Thank you for the feedback, however I decided to simulate again with a vIOS and I received the summary-address as expected, so I guess the issue might be a bug on the initial IOS I was using which was the IOS 15.2 on a 7200.

regards,

Tariq

1 Like

Hello Tariq

Great, that’s for sharing that with us. It’s always valuable to hear the solutions to problems that were faced, that way we can all benefit from the experience.

Thanks again!

Laz