Code Vigorous

Dustin J. Mitchell

IPv6 Configuration

27 Jun 2010

supports IPv6 and I should test that support. It was also a good chance to re-immerse myself in network configuration, and Hurricane Electric has a neat certification process to add some motivation. I began by getting local IPv6 connectivity set up over the HE tunnel, using my Gentoo systems. This was fairly straightforward, as the Gentoo net scripts natively support IPv6. The firewall system I use (Shorewall) does not support IPv6 directly. Instead, there’s a parallel shorewall6 package to install. Aside from the annoyance of setting up two separate firewalls, this did not cause appreciable difficulties. With all of this in place, I was at the “Explorer” level.

The next task was to set up a working IPv6 desktop. My home network uses 802.1q VLAN tagging to layer both an external, publicly routable IPv4 network ( on VLAN 20) and an internal, NAT’d IPv4 network (172.16.1/24 on VLAN 10). I wanted to make VLAN 10 a dual-stack network, rather than invent a new VLAN for my IPv6 network. Initially, I didn’t realize that HE uses, in my case, 2001:470:1f10:826::0/64 just for the tunnel (yes, two addresses out of 264 used – maybe we’ll need IPv8 sooner than we think!). I assumed that the /64 I was allocated was to be used for all of my nodes, and tried to subnet it locally, using 2001:470:1f10:826::0/112 for the tunnel and 2001:470:1f10::1/112 for the internal network. This worked with manual configuration, but radvd seemed to always want to advertise a /64. A little reading about the RA protocol showed this to be correct: RA provides the high 64 bits (the network portion), and the clients provide the low 64 bits using EUI-64. I was stymied until I looked at the tunnel details again and noticed that the “Routed IPv6 Prefixes” section listed a different prefix (2001:470:1f11:826/64).

With this in place, the subnet and firewall setup was a breeze. Using a manual configuration on my MacBook, I was able to communicate via IPv6. However, the stateless autoconfiguration didn’t work. I briefly tried DHCPv6, but Macs do not support it. The RA client correctly combines the network and EUI-64 components to create a full address, and it correctly copies the link-local address of the router, but it does not set up a default route using that router, making the whole thing fairly useless. A trip to #ipv6 confirmed that Macs are, indeed, broken this way, so I stopped worrying about it.

The remainder of the certification process involved getting Apache, Postfix, and Bind speaking IPv6, none of which was very difficult. I did discover that BIND’s $ORIGIN didn’t work correctly. A zonefile with


didn’t work, but spelling out the entire reversed address did. I’m sure this was due to a typo, but several checks didn’t reveal anything.

However, I’m now stuck at the Guru level until GoDaddy starts supporting IPv6 glue for the .us TLD. I feel cheated, somehow!