DMVPN Phase 1 RIP Routing

In the first DMVPN lesson I explained some of its basics, in the second lesson I explained how to create a basic DMVPN phase 1 configuration. In this lesson, we’ll take a look how RIP behaves on DMVPN phase 1.

Here’s the topology we will use:

DMVPN Example Topology loopbacks

Above we have two spoke routers and one hub, our underlay network uses and the overlay network uses Each router has a loopback interface with a network that we can advertise in RIP.


Tunnel Interfaces

Here is the configuration of the tunnel interfaces on the hub and spoke routers. I explained these commands in the DMVPN phase 1 basic configuration lesson so I’m not going to discuss them again:

Hub(config)#interface Tunnel0
Hub(config-if)#ip address
Hub(config-if)#ip nhrp authentication DMVPN
Hub(config-if)#ip nhrp map multicast dynamic
Hub(config-if)#ip nhrp network-id 1
Hub(config-if)#tunnel source GigabitEthernet0/1
Hub(config-if)#tunnel mode gre multipoint
Spoke1(config)#interface Tunnel0
Spoke1(config-if)#ip address
Spoke1(config-if)#ip nhrp authentication DMVPN
Spoke1(config-if)#ip nhrp map
Spoke1(config-if)#ip nhrp map multicast
Spoke1(config-if)#ip nhrp network-id 1
Spoke1(config-if)#ip nhrp nhs
Spoke1(config-if)#tunnel source GigabitEthernet0/1
Spoke1(config-if)#tunnel destination
Spoke2(config)#interface Tunnel0
Spoke2(config-if)#ip address
Spoke2(config-if)#ip nhrp authentication DMVPN
Spoke2(config-if)#ip nhrp map
Spoke2(config-if)#ip nhrp map multicast
Spoke2(config-if)#ip nhrp network-id 1
Spoke2(config-if)#ip nhrp nhs
Spoke2(config-if)#tunnel source GigabitEthernet0/1
Spoke2(config-if)#tunnel destination

Let’s do two quick checks, we want to make sure that both spokes are registered to the hub:

Hub#show dmvpn | begin 192.168.123.
     1    UP 00:22:37     D
     1    UP 00:00:32     D

And we want to make sure that we can ping all tunnel IP addresses:

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to, timeout is 2 seconds:
Success rate is 100 percent (5/5), round-trip min/avg/max = 6/6/8 ms
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to, timeout is 2 seconds:
Success rate is 100 percent (5/5), round-trip min/avg/max = 5/6/9 ms

Now we can focus on the RIP configuration…


Let’s enable RIP on all routers:

Hub(config)#router rip
Hub(config-router)#version 2
Hub(config-router)#no auto-summary
Spoke1(config)#router rip
Spoke1(config-router)#version 2
Spoke1(config-router)#no auto-summary
Spoke2(config)#router rip
Spoke2(config-router)#version 2
Spoke2(config-router)#no auto-summary 

Now let’s see what we have…

Hub#show ip route rip is subnetted, 1 subnets
R [120/1] via, 00:00:07, Tunnel0 is subnetted, 1 subnets
R [120/1] via, 00:00:06, Tunnel0

Our hub router has learned both networks on the loopback interfaces. Take a good look at the next hop IP addresses that we have here, these are the tunnel addresses. When the hub wants to reach these networks, it will have to check NHRP to find the NBMA addresses:

Hub#show dmvpn | begin Hub
Type:Hub, NHRP Peers:2, 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     1    UP 00:29:29     D
     1    UP 00:07:24     D

When we want to reach we will use as the next hop. In our NHRP cache we see that we need to use NBMA address to get there.

What about the spoke routers, did they learn anything?

Spoke1#show ip route rip is subnetted, 1 subnets
R [120/1] via, 00:00:17, Tunnel0
Spoke2#show ip route rip is subnetted, 1 subnets
R [120/1] via, 00:00:08, Tunnel0

Our spoke routers only have one entry, the network on the loopback interface of the hub router. What went wrong here?

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Forum Replies

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

  2. 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 lO0’s as well as the tunnel IP’s

    Thanks you,


  3. Hi Safwan,

    What exactly do you mean with “router interface IP network” ?

    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.


  4. Hi Rene,

    I meant network 192.168.123.x

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