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Here is my problem. I have a server A that has two IP addresses. One public IPv4 and one IPv6.

Server B has only one IPv6 address.

I want to host most of my services on server B (because I have more disk space on it, I can control it better) but I need the IPv4 of the server A. I would like to set up a 4in6 tunnel (RFC 2473) between A and B so that I can transfer the traffic from the IPv4 address in A to B.

If needed, I can request another IPv4 address on the server A, but I'd prefer not to.

My question is: which software use to do the 4in6 tunnelling? I suppose OpenVPN can do the thing, but is there any implementation of the 4in6 protocol on Linux?

A little more challenging: the IPv4 address comes from a venet interface, which cannot be bridged. How could I transfer ownership of this address I don't use on server A to the server B?

Thank you

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It seem that no specific software is required for 4in6 tunnels:

Usage for creating a 4over6 tunnel device (but it's not up afterwards)

# /sbin/ip tunnel add <device> mode ip4ip6 remote <ipv6addressofforeigntunnel> local <ipv6addresslocal>

Usage (generic example for one tunnel):

# /sbin/ip -6 tunnel add ip6tnl1 mode ip4ip6 remote <ipv6addressofforeigntunnel1> local <ipv6addresslocal>
# /sbin/ip link set dev ip6tnl1 up 
# /sbin/ip -6 route add <prefixtoroute1> dev ip6tnl1 metric 1

This doesn't tell me yet how I can forward the IPv4 address of my vmnet device, but at least it now seem easy to create a NAT on server A.

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