IPv4-Mapped IPv6 Address
| IPv6 Address Type: | IPv4 Mapped |
| Prefix: | ::ffff/96 |
| Local Routeable: | Yes |
| Global Routeable: | Yes |
| Global Unique: | Yes |
| Example: | ::ffff:83.90.47.30 |
| IPv4 Equivalent: | None |
| Described in: | rfc4291 |
| rfc4038 section 4.2 | |
These addresses are used to embed IPv4 addresses in an IPv6 address. One use for this is in a dual stack transition scenario where IPv4 addresses can be mapped into an IPv6 address.
See RFC 4038 for more details
IPv4-mapped IPv6 addresses are used in scenarios where IPv6 an IPv6-only application need to communicate with an IPv4 only application using IPv4 packets.
IPv4-mapped address
The IPv4-mapped address, 0:0:0:0:0:FFFF:w.x.y.z or ::FFFF:w.x.y.z, is used to represent an IPv4-only node to an IPv6 node. It is used only for internal representation. The IPv4-mapped address is never used as a source or destination address for an IPv6 packet. The IPv6 protocol does not support the use of IPv4-mapped addresses.[1]
IP Addresses with a Dual-Stack Socket
Dual-stack sockets always require IPv6 addresses. The ability to interact with an IPv4 address requires the use of the IPv4-mapped IPv6 address format. Any IPv4 addresses must be represented in the IPv4-mapped IPv6 address format which enables an IPv6 only application to communicate with an IPv4 node. The IPv4-mapped IPv6 address format allows the IPv4 address of an IPv4 node to be represented as an IPv6 address. The IPv4 address is encoded into the low-order 32 bits of the IPv6 address, and the high-order 96 bits hold the fixed prefix 0:0:0:0:0:FFFF. The IPv4-mapped IPv6 address format is specified in RFC 4291. For more information, see www.ietf.org/rfc/rfc4291.txt. The IN6ADDR_SETV4MAPPED macro in Mstcpip.h can be used to convert an IPv4 address to the required IPv4-mapped IPv6 address format.
If the underlying protocol is actually IPv4, then the IPv4 address is mapped into an IPv4-mapped IPv6 address format. That is the, family field in the SOCKADDR structure indicates AF_INET6, but an IPv4-mapped IPv6 address is encoded in the IPv6 address structure. For a dual-stack socket in listening mode, this means that any accepted IPv4 connections will return an IPv4-mapped IPv6 address. For a dual-stack socket that is connecting to an IPv4 destination, the SOCKADDR structure passed to connect must be an IPv4-mapped IPv6 address. Applications must take care to handle these IPv4-mapped IPv6 addresses appropriately and only use them with dual stack sockets. If an IP address is to be passed to a regular IPv4 socket, the address must be a regular IPv4 address not a IPv4-mapped IPv6 address.[2]
Examples
Only seen working application using IPv4-mapped IPv6 addresses is Windows 7 ping!!!
<input>
C:\Users\Henrik thomsen><notice>ping ::ffff:192.168.139.50</notice>
Pinging 192.168.139.50 with 32 bytes of data:
Reply from 192.168.139.50: bytes=32 time<1ms TTL=62
Reply from 192.168.139.50: bytes=32 time<1ms TTL=62
Reply from 192.168.139.50: bytes=32 time<1ms TTL=62
Reply from 192.168.139.50: bytes=32 time<1ms TTL=62
Ping statistics for 192.168.139.50:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms
</input>or same as
<input>
C:\Users\Henrik thomsen><notice>ping ::ffff:c0a8:8b32</notice>
Pinging 192.168.139.50 with 32 bytes of data:
Reply from 192.168.139.50: bytes=32 time<1ms TTL=62
Reply from 192.168.139.50: bytes=32 time<1ms TTL=62
Reply from 192.168.139.50: bytes=32 time<1ms TTL=62
Reply from 192.168.139.50: bytes=32 time<1ms TTL=62
Ping statistics for 192.168.139.50:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms
</input>