IPv4 and IPv6 Crossplay
Unit: 4
Lesson: 5
i need them both, but on a single network
Most networks run both IPv4 and IPv6 in some or all segments for connectivity and internetworks. This can be works using dualstack hosts, tunneling, or address translation.
Dual Stack
Dualstack hosts are able to run both v4 and v6 at the same time, and are able to communicate with hosts using either version. Most modern OSs support dual stack, and they try to communicate using IPv6 as the default.
The protocol to use depends on the DNS records of the network, since most services are addressed using names instead of IP addresses (e.g.
portainer.raspi.localvs10.0.0.30:9000).
Tunneling (6to4)
Tunneling is sometimes used to deliver v6 packets across an v4 network. It wraps the v6 packet inside of an v4 one, like an envelope. As it's approaching the destination, the v6 packet is unsealed and routed appropriately. This process is slow as the overhead is massive.
6to4 addresses are prefixed with 2002::/16, but it's been replaced with a better protocol called IPv6 Rapid Deployment (6RD). 6RD has various performance improvements over 6to4, and replaces the 6to4 prefix with an ISP-managed one.
Microsoft provides support using it's Teredo protocol, along with its open-source Linux/UNIX equivalent Miredo. Teredo uses
3544/udp, and it requires compatible clients and servers.
Tunneling is also possible using GRE. GRE allows Network layer protocols to be wrapped in virtual P2P links, leveraging the advantage that it was designed for v4 and is widely supported, and that it's able to carry both v4 and v6 packets.
Network Address Translation for IPv6 (NAT64)
NAT is responsible for rewriting addresses as they cross network boundaries. Using NAT64, v6 hosts address v4 hosts using a specialized v6 address. That address is prefixed with 64:ff9b::/96 along with the 32-bit v4 address, hence the 64 in NAT64. When the packet reaches the gateway, the router extracts the v4 address from the packet and forwards it to it's corresponding host. Replies from the v4 host to the v6 one are tracked using Transport layer port numbers.
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