Site-to-Site VPN, or: IPSec via IPv6

Hey there,

more and more IPv6 addresses are assigned, and since we are using IPSec-tunnels to encrypt the traffic between our branch-offices, I was wondering ‘how far has the support for IPSec via IPv6 come’?

So, I checked it out, using our Astaro (now Sophos) Firewall at work and my M0n0wall at home.

First of all, you of course need IPv6 activated on both ends and need an active connection. Wether you get that native from your provider or, for example, through is up to you. If you see fe80:… addresses: These are the link local addresses and do not work for us here.

Setup on the Astaro (Sophos UTM):

  • Go to ‘Site-to-Site VPN’ -> ‘IPSec’, create a ‘Remote Gateway’. We use a Preshared Key for our test setup now, in a real setup you might want to use RSA or a certificate. For the gateway you use the IPv6 WAN address of the m0n0wall. Oh, and don’t forget to add the remote networks. (This can be the whole /48 for example, no need to use several /64).
  • Then go to ‘Connections’ and create a new connection, using our just created gateway. I use TrippleDES for a policy here.
  • If you hit ‘automatic firewall rules’ your remote network gets full access to your local network. If this is unwanted, don’t do it! You can create the rules you like under ‘Network Security’ -> ‘Firewall’

All done here!

Setup on the M0n0wall:

  • Go to ‘VPN’ -> ‘IPSec’ and click the + symbol to create a new tunnel
  • For the interface chose ‘WAN’, unless you are routing internal or something (the interface should have the same IP that you chose for the remote gateway on the Astaro).
  • Enter your local subnet, I chose my /48 here.
  • Enter remote gateway (again, WAN IPv6 from the astaro)
  • Phase 1: Use 3DES, MD5, DH Keygroup 5, Lifetime 7800, PreShared Key
  • Phase 2: 3DES, MD5, Lifetime 3600

These are the values taken from the pre-existing definition for 3DES on the Astaro. You could change that, but do it on both sides.

Now just create rules what traffic you want to allow through the tunnel and which not. Remember: Both sides must fit in order for traffic to go through.

All save, all encrypted, all IPv6.

Voilà: Enjoy your Site-to-Site IPv6 tunnel.


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