R3303-HP HSR6800 Routers Layer 3 - IP Services Configuration Guide

205
Configuring AFT
Overview
Address Family Translation (AFT) is a transition technology for communication between IPv4 and IPv6
networks.
As shown in Figure 85, the AFT
router performs address and protocol translation between IPv4 and IPv6
networks. With AFT, IPv6 and IPv4 hosts can communicate with one another without having their
configurations changed.
AFT allows an IPv6 host to initiate communication with any IPv4 host, but allows an IPv4 host to initiate
communication with only IPv6 hosts whose addresses are IVI addresses. For information about IVI
addresses, see "IVI prefix and IVI address."
Figure 85 AFT network diagram
Basic concepts
This section covers basic AFT concepts.
DNS64 prefix
A DNS64 prefix is an IPv6 address prefix used to translate IPv4 addresses into IPv6 addresses. The
length of a DNS64 prefix can be 32, 40, 48, 56, 64, or 96 bits, as shown in Figure 86. T
he address
translation methods vary depending on the length of the DNS64 prefix.
• If the length of the DNS64 prefix is 32, 64, or 96 bits, the IPv4 address is added to the IPv6 address
as a whole.
• If the length of the DNS64 prefix is 40, 48, or 56 bits, the IPv4 address is separated by the bits 64
through 71.