DMVPN supports three different versions called “phases”. In my first DMVPN lesson I explained the basics and the DMVPN phase 2 configuration and DMVPN phase 1 configuration lessons explain how to configure the first two phases.
This time, I’ll show you how to configure DMVPN phase 3. We’ll use the following topology for this:
We have one hub router and two spoke routers.
Configuration
The configuration of DMVPN phase 3 and 2 is very similar. Let’s start with the following DMVPN phase 2 configuration on all routers:
Hub(config)#interface Tunnel0
Hub(config-if)#ip address 172.16.123.1 255.255.255.0
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 172.16.123.2 255.255.255.0
Spoke1(config-if)#ip nhrp authentication DMVPN
Spoke1(config-if)#ip nhrp map 172.16.123.1 192.168.123.1
Spoke1(config-if)#ip nhrp map multicast 192.168.123.1
Spoke1(config-if)#ip nhrp network-id 1
Spoke1(config-if)#ip nhrp nhs 172.16.123.1
Spoke1(config-if)#tunnel source GigabitEthernet0/1
Spoke1(config-if)#tunnel mode gre multipointSpoke2(config)#interface Tunnel0
Spoke2(config-if)#ip address 172.16.123.3 255.255.255.0
Spoke2(config-if)#ip nhrp authentication DMVPN
Spoke2(config-if)#ip nhrp map 172.16.123.1 192.168.123.1
Spoke2(config-if)#ip nhrp map multicast 192.168.123.1
Spoke2(config-if)#ip nhrp network-id 1
Spoke2(config-if)#ip nhrp nhs 172.16.123.1
Spoke2(config-if)#tunnel source GigabitEthernet0/1
Spoke2(config-if)#tunnel mode gre multipointTo migrate from DMVPN phase 2 to 3, we only need two commands…here’s the first command:
Hub(config)#interface tunnel 0
Hub(config-if)#ip nhrp redirect The NHRP redirect command on the hub will inform spoke routers that they can reach another spoke router directly. The second command is needed on the spoke routers:
Hi !
I didnt have “ip nhrp redirect” in my IOS (C3745-ADVENTERPRISEK9_SNA-M) ??? that´s the only one i got…
/Oskar
Hello,
Should router do icmp redirection to his neighbors when they are in one subnet? This feature of IP protocol doesn’t work in this case, does it?
I see that you disable icmp redirects by issuing “no ip redirects” command on Tunnel interface.
Hi Rene, may be a trivial question but I have not played with GNS3 much. How do you simulate cloud like in this topology?
Hello Rene,
First, thanks for your great job! it’s really simple to understand
I have a problem with the configuration of the phase 3 DMVPN in GNS3. Since i type the 'ip nhrp redirect’command, i have te following error message ‘% NHRP-WARNING: ‘ip nhrp redirect’ failed to initialise’
Could you please tell me why? I use the 7200 ios version 15.2.
Thanks for your reply
Hi Renee!
Great lesson as always
I was just wondering what about the “ip nhrp server-only” what is the purpose of the command??
-Dan