Can i use a proxy from ipv6 to ipv4

There are a number of approaches for running IPv6 only networks but still allowing access to services that are only available via IPv4.

If you want to use a HTTP proxy from a IPv6 only device to access IPv4 devices then the proxy device will need both an IPv4 and an IPv6 address (Dual Stack).

The more effective approach is to take a similar approach as most Home networks and use a form of NAT (Network Address Translation) as this allows all protocols to work, not just HTTP. This is called NAT64 which makes use of a single device at the edge of the network which translates requests from IPv6 to IPv4 and the responses back again.

To make this work you also need to re-map DNS look ups, because if a hostname only has IPv4 address then the IPv6 client won't know where to connect to. So this requires running a special DNS server (called DNS64).

The flow is as follows

• Client looks up the IPv6 address of the service
• If the DNS64 server can only find a IPv4 address is will pre-pend a specific IPv6 prefix to the address to build a full IPv6 address. The default prefix is 64:ff9b::/96.
• The network is configured to route all addresses starting with this prefix to a specific machine at the edge of the network that also has a IPv4 connection.
• This machine uses NAT64 to strip off the IPv6 prefix and translate the source address to it's IPv4 address (storing the original source IPv6 address in a lookup table.).
• When the service replies the NAT64 device remaps the destination to the original IPv6 source address and re-applies the prefix to the source address.

I have a blog post with more details here.