How to I forward requests on a IPv6 port to a IPv4 host behind NAT?

Question

I run a Xen Dom0 with 2 VMs NATted (other VMs are bridged, and are ok).

This Dom0 has an IPv6 and IPv4 address. Requests to, for example port 25 are forwarded to a LAN address that one of the VMs handle.

For example:

VM_DNS_MAIL=172.16.1.1
iptables -t nat -A PREROUTING -d 1.2.3.4/26 -p tcp --dport 25 -j DNAT --to $VM_DNS_MAIL
iptables -t nat -A PREROUTING -d 1.2.3.4/26 -p tcp --dport 53 -j DNAT --to $VM_DNS_MAIL

1.2.3.4 being my public IP of the Dom0.

This works perfectly with IPv4. How can I achieve the same with IPv6?

Answer 1

Don't. Get a routed netblock of v6 space, or sub-subnet your existing one, and give the routed VMs real routed v6 addresses.

Answer 2

I have experience with IPv6 to IPv4 NAT, and there are some issues with fragmentation. It is better to use a reverse proxy like haproxy.