DMVPN Phase 1 RIP Routing

Lessons Discussion
1

This topic is to discuss the following lesson:

2

Hallo Rene how did u config the tunnel?because it got the ip address of 172.16.123.in your configuration u only did HUB and the 2 SPOKES

3

Hereā€™s the basic DMVPN phase 1 configuration that I used for this:

https://networklessons.com/security/dmvpn-phase-1-basic-configuration/

4

Hi Rene,

Would you kindly help explain, where is the router interface IP network in RIP and how does it fit in the dynamic routing protocol as we only advertised the lO0ā€™s as well as the tunnel IPā€™s

Thanks you,

Safwan

5

Hi Safwan,

What exactly do you mean with ā€œrouter interface IP networkā€ ?

By advertising the loopback interfaces and enabling RIP on the tunnel interfaces, we have everything we need for the routers to learn each others loopback networks.

Rene

6

Hi Rene,

I meant network 192.168.123.x

7

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

Thatā€™s all we need for DMVPN, connectivity between the NBMA addresses so that we can establish the tunnels.

8

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

9

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)

10

@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

11

@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

12 
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.

13

Hi Dionisis,

Thatā€™s right, EIGRP changes it.

Rene

14

Hi

please check the attached clip, here ā€˜no ip split-horisonā€™ or jest ā€˜ip split-horisonā€™.?

15

Hi Noorudheen,

I donā€™t see an attachment but the command is no ip split-horizon.

Rene

16

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

One more confusion regarding the output ā€¦

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

17

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

18

Hi,

In one of last capture images, the lesson says : ā€œAbove you can see the NBMA addressesā€. 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 ā€œpublicā€ networks learned by the Spoke) ?

19

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

20

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 ā€œkind-of Frame-Relay networkā€ DMVPN builds on the underlay Network.