[CentOS] IPv6 forwarding and ip6tables

Robert Moskowitz rgm at htt-consult.com
Tue Dec 30 17:54:24 UTC 2008

I am running multiple IPv6 subnets here in my testbed.  My IPv6 'router' 
is a Centos box with IPv6forwarding turned on.  It is also my RADVD 
server (over multiple VLans), and Miredo server/relay.

I thought I had a simple ip6table setup that protected the box and let 
it forward.  Well I am wrong.

I got my previous DNS over IPv6 working on the DNS server, then tried to 
get it working from another box.  After a couple hours fighting with it, 
I finally figured out that my Centos IPv6 router was rejecting the 
IPv6DNS queries, not forwarding them.  I turned off ip6tables and the 
DNS lookups worked just fine.

So I thought, well Shorewall6 beta is out, let's go with it already.  I 
check out the shorewall discussions and discover you need at least the 
2.6.25 kernel for Shorewall6.  When I mentioned my dilemma, I was told 
that "2.6.18 doesn't support stateful IPv6 firewalling at all!"

Just great......   When is that Centos 6 going to happen????  :(

Anyway, the challenge for now:

What do I put into ip6tables so that any IPv6 traffic that comes in any 
of the vlans on eth1 can go out any of the vlans on eth1?

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