DMVPN Phase 3 Basic Configuration

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:

dmvpn-example-topology

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 multipoint
Spoke2(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 multipoint

To 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:

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Forum Replies

  1. Hi !

    I didnt have “ip nhrp redirect” in my IOS (C3745-ADVENTERPRISEK9_SNA-M) ??? that´s the only one i got…

     

    /Oskar

  2. Hi Rene,

    What is the advantages using the Phase 3 over Phase 2?

    Try to minimize the routing entry in the spoke router?

    Davis

  3. Hi Davis,

    The main advantage is that you have smaller routing tables. In phase 2, each spoke router requires specific entries for networks it wants to reach behind other spoke routers. With phase 3, a summary route is all you need.

    Rene

  4. Hi Rene,

    ok. Thanks

    Davis

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