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What is IPv6; interoperability methods

Short answer

IPv6 is 128-bit protocol with fixed header, IPsec, autoconfiguration. Interoperability methods: dual stack (both stacks), tunneling (IPv6 in IPv4), header translation (NAT64), application proxies. Dual stack most common.

What is IPv6? What methods are used so that IPv6 and IPv4 networks are interoperable?

IPv6 is the sixth version of the Internet Protocol (RFC 8200) with 128-bit addresses (written in hexadecimal, e.g. 2001:0db8::1), a fixed 40-byte header, built-in security (IPsec), autoconfiguration, flow labels and no broadcast. It was designed to replace IPv4. IPv4 and IPv6 are not directly compatible, so interoperability methods are used while the Internet moves from one to the other.

Methods

  1. Dual stack: devices run both protocol stacks and talk IPv4 with IPv4 nodes and IPv6 with IPv6 nodes. DNS gives A or AAAA records.
 +-------------------+
 | Application       |
 | IPv4  |   IPv6    |
 | Data link / PHY   |
 +-------------------+
  1. Tunneling: IPv6 packets are carried inside IPv4 packets across IPv4-only networks. Variants: manually configured tunnels, 6to4, ISATAP, Teredo (through NAT).
IPv6 island --R1==[IPv6 inside IPv4]==R2-- IPv6 island
  1. Header translation (protocol translation): a gateway converts the headers between IPv4 and IPv6, for example NAT64 with DNS64, so an IPv6-only host can reach an IPv4-only server.
  2. Application-level proxy gateways can also relay between the two (for example a proxy that accepts IPv6 clients and connects to IPv4 servers).

Dual stack is the most widely used; the others solve special cases.

✓ Answer checked by Claude Opus 5.5 (high effort)

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