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IPv6 transition mechanisms
4in6 Tunneling from IPv4 to IPv6
6in4 Tunneling from IPv6 to IPv4
6over4 Transport of IPv6 data packets between dual-stack nodes over an IPv4 network
6to4 Transport of IPv6 data packets over an IPv4 network (obsolete)
AYIYA Anything In Anything
Dual stack Network nodes with IPv4 and IPv6 in parallel operation
Dual-Stack Lite (DS-Lite) Like dual stack, but with global IPv6 and carrier NAT IPv4
6rd IPv6 rapid deployment
ISATAP Intra-Site Automatic Tunnel Addressing Protocol (deprecated)
Teredo Encapsulation of IPv6 packets in IPv4 UDP -Datenpaketen
NAT64 Translation of IPv4 addresses into IPv6 addresses
464XLAT Translation from IPv4 to IPv6 to IPv4 addresses
SIIT Stateless IP / ICMP translation

6in4 (tunneling from IPv6 to IPv4) is an IPv6 transition mechanism for the transmission of IPv6 data packets between IPv6 nodes connected via an IPv4 network.


With 6in4, the data traffic is packed into IPv4 data packets, the protocol number of which has the decimal value 41 in the IP header . The transported IPv6 data packet follows the IPv4 header directly. The IPv4 header only increases the data packet by 20 bytes. With a Maximum Transmission Unit (MTU) of 1500 bytes, as is the case with standard Ethernet connections, IPv6 frames with 1480 bytes can be transported without fragmentation . Like all proto-41 tunnels, 6in4 tunnels are static, i.e. the end points are configured statically.



  • RFC 4213 , Basic Transition Mechanisms for IPv6 Hosts and Routers

Individual evidence

  1. RFC 2473 , Generic Packet Tunneling in IPv6 , Section 5