R3721-F3210-F3171-HP High-End Firewalls VPN Configuration Guide-6PW101

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IPv6 address of each CPE so that IPv4 networks connected to different CPEs can use the same
address space.
• DS-lite tunnel—The IPv4 over IPv6 tunnel between the CPE and AFTR which carries IPv4 packets
over an IPv6 network.
Figure 70 Packet forwarding process in DS-lite
When a gateway serves as the CPE, the changes of source and destination IP addresses and port
numbers are illustrated in Figure 70. T
he entire process is summarized as follows:
• The CPE and AFTR encapsulate and de-encapsulate packets.
• The AFTR performs NAT.
When a host serves as the CPE, the process is similar and therefore not shown.
NOTE:
• NAT supports both basic address translation between private and public addresses and Network
Address Port Translation (NAPT), which translates both IP address (private or public) and port
number. Figure 70 sh
ows an example of NAPT. For more information about NAT, see NAT
Configuration Guide
.
• DS-lite tunnel supports only an IPv4 host in a private network initiatin
g
communication with an IPv4 hos
t
on the Internet and does not support an IPv4 host on the Internet initiatin
g
communication with an IPv4
host in a private network.