Prefix Translation - HPE FlexNetwork HSR6800 Configuration Manual

1. When an IPv6 host first initiates a connection to the IPv4 network, it creates a mapping from the
host's IPv6 address to an IPv4 address and a port block.
2. It translates the IPv6 address to the IPv4 address, and the source ports to ports in the port block
for subsequent connections from the IPv6 host until the ports in the port block are exhausted.
NOTE:
If the port range cannot be divided by the port block size exactly, the remaining ports are not used for
translation.

Prefix translation

NAT64 prefix translation
NAT64 prefix is an IPv6 address prefix used to construct an IPv6 address representing an IPv4 node
in an IPv6 network. The IPv6 hosts do not use a constructed IPv6 address as their real IP address.
The length of a NAT64 prefix can be 32, 40, 48, 56, 64, or 96.
As shown in
64 through 71 in the constructed IPv6 address are reserved bits and must always be zero.
•
If the prefix length is 32, 64, or 96 bits, the IPv4 address contained in the IPv6 address will be
integral.
•
If the prefix length is 40, 48, or 56 bits, the IPv4 address contained in the IPv6 address will be
divided into two parts by bits 64 through 71.
Figure 147 IPv6 address construction with NAT 64 prefix and IPv4 address
AFT uses a NAT64 prefix to perform the following translation:
•
IPv4-to-IPv6 source address translation. AFT translates a source IPv4 address to an IPv6
address that is created by using the NAT64 prefix and the IPv4 address.
•
IPv6-to-IPv4 destination address translation. AFT uses the NAT64 prefix to match destination
IPv6 addresses and extracts the embedded IPv4 address from matching IPv6 addresses.
A NAT64 prefix cannot be on the same subnet as any interface on the device.
IVI prefix translation
An IVI prefix is a 32-bit IPv6 address prefix. An IVI address is the IPv6 address that an IPv6 node
uses. As shown in
Figure 148 IVI address format
AFT uses an IVI prefix for IPv6-to-IPv4 source address translation. If a source IPv6 address matches
the IVI prefix, AFT translates it to the embedded IPv4 address.
Figure 147, the construction methods vary depending on the NAT64 prefix length. Bits
Figure 148, the IVI address includes an IVI prefix and an IPv4 address.
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