DMVPN IPv6 over IPv4

Lessons Discussion
1

This topic is to discuss the following lesson:

2

Hi Rene
i suspect a typo error:

Spoke1(config-if)#ipv6 nhrp map 2001:DB8::1/128 192.168.123.1

should be

Spoke1(config-if)#ipv6 nhrp map 2001:DB8::1/64 192.168.123.1

same for spoke2

thank you to confirm

Cheers

3

Hi Fethi,

The /128 addresses are correct. It’s a specific mapping between the IPv6 address and the IPv4 address.

Rene

4

Hi
Is possible to transport ipv4 and ipv6 addresses in the same tunnel interface?

If I debug the tunnel of the hub with debug tunnel comand , I recive this output.

R1-Hub#ping 2001:db8::2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:DB8::2, timeout is 2 seconds:

*Apr 20 12:36:50.128: Tunnel0: Drop, Encap failed, pak if = Tunnel0,desthost 0.0.0.0, linktype 79.
*Apr 20 12:36:52.133: Tunnel0: Drop, Encap failed, pak if = Tunnel0,desthost 0.0.0.0, linktype 79.
*Apr 20 12:36:53.224: Tunnel0: Drop, Encap failed, pak if = Tunnel0,desthost 0.0.0.0, linktype 74
*Apr 20 12:36:54.137: Tunnel0: Drop, Encap failed, pak if = Tunnel0,desthost 0.0.0.0, linktype 79.
*Apr 20 12:36:56.139: Tunnel0: Drop, Encap failed, pak if = Tunnel0,desthost 0.0.0.0, linktype 79.
*Apr 20 12:36:58.143: Tunnel0: Drop, Encap failed, pak if = Tunnel0,desthost 0.0.0.0, linktype 79.
Success rate is 0 percent (0/5)
R1-Hub#

Thanks

EDIT…

I was able to configure the ipv6 and ipv4 in the same tunnel.

R1-Hub#show dmvpn 
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
        N - NATed, L - Local, X - No Socket
        T1 - Route Installed, T2 - Nexthop-override
        C - CTS Capable
        # Ent --> Number of NHRP entries with same NBMA peer
        NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
        UpDn Time --> Up or Down Time for a Tunnel
==========================================================================

Interface: Tunnel0, IPv4 NHRP Details 
Type:Hub, NHRP Peers:2, 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     1 192.168.123.2      172.16.123.2    UP 09:28:14     D
     1 192.168.123.3      172.16.123.3    UP 09:26:32     D

Interface: Tunnel0, IPv6 NHRP Details 
Type:Hub, Total NBMA Peers (v4/v6): 2
    1.Peer NBMA Address: 192.168.123.2
        Tunnel IPv6 Address: 2001:DB8::2
        IPv6 Target Network: 2001:DB8::2/128
        # Ent: 1, Status: UP, UpDn Time: 09:31:36, Cache Attrib: D
    2.Peer NBMA Address: 192.168.123.3
          
R1-Hub#
5

Hello Giovanni

It is possible to tunnel both IPv4 and IPv6 over the same GRE tunnel, and since DMVPN is based on GRE, it can be done, as you yourself have provided with your configuration.

Can you share with us the difference between your configurations when you received the “Encap failed” message and the successful tunneling of both protocols?

Thanks!

Laz

6

The log message was caused by a wrong configuration on Spokes.
The command below was missing in the tunnel configuration.

ipv6 nhrp nhs 2001:DB8::1
7

Hello Giovanni

Ah, perfect, thanks for clarifying that. That’s useful information for all of our readers.

Thanks for being a valuable member!

Laz

1 Like
8

Hi @ReneMolenaar @lagapidis ,

When we have to use tunnel mode gre multipoint ipv6 command?

9

Hello Nipun

The example in the lesson is encapsulating IPv6 packets into an IPv4 tunnel. In this example, the underlay network is based on IPv4 while the overlay network is IPv6.

The tunnel mode gre multipoint command must know into what type of IP packet the encapsulation will take place. The type of IP packet is that of the underlay network.

So, if the lesson was reversed, and you had IPv6 running on the underlay and IPv4 running on the overlay, then you would need the tunnel mode gre multipoint ipv6 with the ipv6 keyword at the end. Otherwise, if it is not specified, IPv4 is the default.

I hope this has been helpful!

Laz