IPv4 addresses will still need to be used on networks for the foreseeable future to enable end users who cannot connect using IPv6 to fully access the Internet. Using IPv4 and IPv6 addresses in parallel is known as dual stacking. Devices and connections that are dual stacked can communicate over both IPv4 and IPv6.

The technologies listed below maintain connectivity to IPv4 hosts by sharing IPv4 addresses between clients and provide a mechanism to connect to emerging IPv6-only networks.

Don’t know which technology to use for your network? Try our IPv6 Transition Decision Tree.

There are many other IPv6 transition technologies. We’ve listed the ones that are most used below:


Transporting IPv6 in IPv4:

Transporting IPv6 in UDP

Transporting IPv4 in IPv6


Translating IPv6 into IPv4:



  • Use manually configured tunnels towards a fixed tunnel broker like SixXs, Hurricane Electric, or your own system
  • Stable and predictable but not easily deployed to large end user networks
  • Maximum Transmission Unit (MTU) might cause issues

Links: UKERNA IPv6 Technical Guide


  • An “Automatic” tunnel, the system can configure itself
  • The IPv4 address is part of the IPv6 address
  • Requires a public IPv4 address
  • Uses anycast to reach a nearby server
  • Return traffic might choose another server

Links: What is 6to4? | UKERNA IPv6 Technical Guide


  • Is quite similar to 6to4
  • Encodes the IPv4 address in the IPv6 prefix
  • Uses the address space assigned to the operator
  • The operator has full control over the relay
  • Traffic is symmetric across a relay, or at least stays in your domain
  • Can work with both public and private space
  • Needs additional software for signalling



  • Uses User Datagram Protocol (UDP) to encapsulate IPv6 packets
  • Works across (most) NAT implementations

Links: List of Teredo serversTeredo Overview


  • Tunneling IPv4 over IPv6
  • Allows clients to use RFC1918 addresses without doing NAT themselves
  • NAT is centrally located at the provider
  • The client’s IPv6 address is used to maintain state and to keep clients apart
  • Allows for duplicate IPv4 ranges

Links: Understanding DS-lite



  • Single-stack clients will only have IPv6
  • Translator box will strip all IPv6 headers and replace them with IPv4 headers
  • Requires some DNS manipulation
  • Capture responses and replace A records with AAAA records
  • Response is crafted based on target IPv4 address
  • Usually means that IPv4 addresses need to be shared

Links: Cisco – NAT64 Configuration