Ok, so I have nice Ubuntu 12.04 headless server running. It's very happy. It's my router/firewall/DNS/etc. eth0 is WAN, eth1 is LAN.
I can easily get my IPv6 tunnel connected, and my server will continue to work just fine, and sees & browses both ip4 & ip6 sites. Yay.
But if ip6 is running, I can not, for the life of me, get the rest of my network to browse anything.
But if I roll back the changes, my network is fine.
DNS seems to still work, as I can ping from a client machine & it will resolve the address, but it won't actually return pings.
What information can I give that will help y'all help me?
My guess is it's not bridging from eth1 to eth0 properly after I add ip6. But I can't figure out why the ip4 bridge breaks.
Did you tell the server to be an ipv6 gateway?
As best as I knew how, yea.
I set the sysctrl.conf file to forward ip6 packets, and I also used webmin to tell it act as a router.
If it was ONLY the ip6 traffic that wouldn't get out, I'd understand. But it kills ALL my traffic from my internal network (a win7, win8, googleTV, and android phones, and LinuxMint system).
Got an answer over here: http://askubuntu.com/questions/235919/why-does-ipv6-kill-my-network-in-ubuntu-12-04
In short - badly misconfigured interfaces file.
Interesting reply over there...
Just to add - you're not bridging eth0 and eth1 you're routing IPv4 between them. You're routing IPv6 between he-ipv6 and eth1. You use the tunnel client IPv6 address on your tunnel interface and your routed /64 (or a /64 out of your routed /48) on your LAN interface. If you look on your tunnel details page you'll see those subtle address differences highlighted in bold.
It's a common mistake that a lot of us have made but we soon learn from it ;)