IPv6 Tunneling Part 2: IPv6 Over IPv4 GRE Tunnels

Hello Followers,

 

In this post we will cover the second tunneling technique of this series of posts of IPv6.

This time we will transport our IPv6 traffic inside a GRE packet.

If you want to review the first tunneling technique, check our previous post about IPv6 tunneling.

 

2) IPv6 over IPv4 GRE Tunnels

The real benefit of running this type of tunnel is the fact that you will be able to encapsulate any traffic other than IPv6 and you will also have support for IPSec (if needed).

Just like the first type of VPN we talked about this are Point-To-Point in nature.

Now let’s get our hands dirty by configuring using the same Lab Scenario than before.

 

Screen Shot 2015-07-29 at 4.32.24 PM

 

As we see in the diagram we have 3 Routers (R1,R2 and R3)

  • R1 runs IPv6 in it’s Loopback 1 interface and IPv4 in it’s connection to R2
  • R2 only runs IPv4
  • R3 runs IPv6 in it’s Loopback 1 interface and IPv4 in it’s connection to R2
  • The idea of the Lab is to make sure the Loopback of R1 can communicate with the Loopback of R3

 

 

R1

interface Tunnel1

no ip address

ipv6 address 2001:AAAA:AAAA:AAAA::1/64

ipv6 ospf 100 area 0

tunnel source FastEthernet0/0

tunnel destination 13.0.0.1

tunnel mode gre ip

R3

interface Tunnel1

no ip address

ipv6 address 2001:AAAA:AAAA:AAAA::3/64

ipv6 ospf 100 area 0

tunnel source FastEthernet0/0

tunnel destination 12.0.0.1

tunnel mode gre ip

As you can see the only difference relies in the command “tunnel mode gre ip“. Remember we are trying to encapsulate IPv6 inside an IPv4 GRE packet (that’s why we use tunnel mode gre ip and not tunnel mode gre ipv6).

Verification Stage:

We are still running OSPF between the sites as we did in the first part of this tunneling series and now it’s just time to test connectivity between the sites.

R3#ping 2001:AAAA:BBBB:CCCC::1 source loopback 1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 2001:AAAA:BBBB:CCCC::1, timeout is 2 seconds:

Packet sent with a source address of 2001:BBBB:CCCC:DDDD::1

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 16/20/24 ms

R3#sh ipv6 route 2001:AAAA:BBBB:CCCC::/64 longer-prefixes

IPv6 Routing Table – 7 entries

Codes: C – Connected, L – Local, S – Static, R – RIP, B – BGP

       U – Per-user Static route

       I1 – ISIS L1, I2 – ISIS L2, IA – ISIS interarea, IS – ISIS summary

       O – OSPF intra, OI – OSPF inter, OE1 – OSPF ext 1, OE2 – OSPF ext 2

       ON1 – OSPF NSSA ext 1, ON2 – OSPF NSSA ext 2

O   2001:AAAA:BBBB:CCCC::1/128 [110/11111]

     via FE80::C201:2FF:FE37:0, Tunnel1

R3#sh int tunnel 1

Tunnel1 is up, line protocol is up

  Hardware is Tunnel

  MTU 1514 bytes, BW 9 Kbit/sec, DLY 500000 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation TUNNEL, loopback not set

  Keepalive not set

  Tunnel source 13.0.0.1 (FastEthernet0/0), destination 12.0.0.1

  Tunnel protocol/transport GRE/IP

That’s it!! We just tested connectivity and we also confirmed that the IPv6 traffic is being encapsulated by GRE/IP.

I hope you liked this post.

Regards,

Jcarvaja