4in6

4in6 refers to tunneling of IPv4 in IPv6.^[1][2] It is an Internet interoperation mechanism allowing Internet Protocol version 4 (IPv4) to be used in an IPv6 only network. 4in6 uses tunneling to encapsulate IPv4 traffic over configured IPv6 tunnels as defined in RFC 2473.^[3] 4in6 tunnels are usually manually configured but they can be automated using protocols such as TSP to allow easy connection to a tunnel broker.^[4]

References

1. Blanchet, Marc (18 May 2009). Migrating to IPv6: A Practical Guide to Implementing IPv6 in Mobile and Fixed Networks. John Wiley and Sons. pp. 345–350. ISBN 9780470468906.
2. Stockebrand, Benedikt (28 November 2006). IPv6 in Practice: A Unixer's Guide to the Next Generation Internet. Springer Science & Business Media. pp. 170–172. ISBN 9783540480013.
3. Conta, Alex; Deering, S. (1998). "RFC 2473: Generic Packet Tunneling in IPv6 Specification". tools.ietf.org. doi:10.17487/RFC2473. Retrieved 17 June 2016.
4. Hagen, Silvia (9 June 2014). Ipv6 Essentials. "O'Reilly Media, Inc.". pp. 228–231. ISBN 9781449335267.