F3726, F3211, F3174, R5135, R3816-HP Firewalls and UTM Devices VPN Configuration Guide-6PW100

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584BDNS64 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
1014HFigure 298. The 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.
Figure 298 DNS64 prefix is added to an IPv4 address to translate it into an IPv6 address
When an IPv4 packet is sent from an IPv4 host to an IPv6 host, AFT translates its source IPv4 address to
an IPv6 address by adding a DNS64 prefix.
When an IPv6 host sends a packet to an IPv4 host, the destination IPv6 address is formed by adding the
DNS64 prefix to the IPv4 address of the IPv4 host. When the AFT receives such a packet, it extracts the
IPv4 address from the IPv6 destination address so that the packet can be forwarded to the IPv4 host.
585BIVI prefix and IVI address
An IVI prefix is a 32-bit IPv6 address prefix. An IVI address comprises an IVI prefix and an IPv4 address,
with bits 32 to 39 set to all 1s, as shown in
1015HFigure 299.
Figure 299 IVI address format
If the source IPv6 address of an IPv6 packet sent from an IPv6 host to an IPv4 host is in the IVI address
format, AFT translates the source IPv6 address to the IPv4 address contained in the source IPv6 address.
For an IPv4 packet sent from an IPv4 host to an IPv6 host, AFT translates its destination IPv4 address to
an IPv6 address by adding an IVI prefix to the IPv4 address.
An IVI address is an IPv6 address that is actually used by an IPv6 host. However, an IPv6 address with
a DNS64 prefix is merely a translated IPv6 version of an IPv4 address and is not used by any host.
282BAFT modes
AFT can be stateless or stateful:
• Stateless AFT