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Service Tests Subjects Nameservers, Webserver, Mailserver Connection, DNS Resolver Connection, DNS Resolver, Reverse DNS, ICMP, Ping, Speed, Webserver



  • IPv4 World ↔ relay2002:x.x.x.x::/48 ↔ IPv6 World
  • is an anycast address of the nearest 6to4 relay
  • 2002:x.x.x.x::/48 is an anycast route of the nearest 6to4 relay
  • On one side of the IPv4 net is an 6to4 relay, on the other an 6to4 router or host
  • IPv4 Hosts get an IPv6 Net
  • IPv6 Hosts get nothing (they know “I'm talking to an 'IPv4 host'” but they don't get an IPv4 IP/Net)
  • IPv6 encapsulated in IPv4
    IPv4(Type=41, Src=x.x.x.x, Dst=, Payload=IPv6(Src=2002:x.x.x.x, Dst=Dst))
  • 2002::/16 gets an public IPv4 Address appended ⇒ 2002:x.x.x.x::/48 ⇒ 16 Bit remaining for subnets.
  • Unmanaged: Automatically finds nearest Router per anycast
  • As an public IPv4 is required, it's hard to NAT
Host IPv4 only Net 6to4 relay At least IPv6 Net
At least IPv6 Net 6to4 router
IPv6(Src=2002:x.x.x.x::, Dst=y) IPv4(Type=41, Src=x.x.x.x, Dst= + IPv6(Src=2002:x.x.x.x::, Dst=y) IPv6(Src=2002:x.x.x.x::, Dst=y)
IPv6(Src=y, Dst=2002:x.x.x.x::) IPv4(Type=41, Src=, Dst=x.x.x.x) + IPv6(Src=y, Dst=2002:x.x.x.x::) IPv6(Src=y, Dst=2002:x.x.x.x::)


  • Like 6to4, but with explicitly configured relays (managed)
  • On both sides of the IPv4 only net are relays or hosts
  • Both have to configure the IPv4 IP of the other endpoint ⇒ Only usable for static IPv4 addresses.
  • Not dependent on an 2002::/16 net


  • Solves the NATing problems of 6in4 and 6to4 by using NATable transport protocols (UDP, TCP, SCTP)
  • Prevents spoofing by signing packages
  • Prevents replaying
  • Does not encrypt packages
  • Still has problems with dynamic IPv4 addresses (those transport protocols does not support roaming)


  • Software/Protocol developed by SixXS to make 6in4 and AYIYA usable for dynamic IPv4 addresses (informs the other endpoint about new IPv4 address)
  • Also used by HE

Address Embedding

  • IPv6 representations of IPv4 addresses
  • IPv4-Mapped IPv6 Address: ::FFFF:x.x.x.x
    • Only on one host
    • Use IPv6 API for IPv4 (prevents duplicated or complicated code)
    • Can never be seen on the wire
  • IPv4-Compatible IPv6 Address: ::x.x.x.x(deprecated)
    • Can be routed and translated to the corresponding IPv4 (and back???)
    • Can be seen on the wire
computer/ipv6.txt · Last modified: 2020-11-18 18:11 by