HP FlexNetwork MSR2003 Configuration Manual page 304

Figure 120 Packet forwarding process in DS-Lite
10.0.0.1/24
10.0.0.2/24
Private
IPv4 network
IPv4 host
IPv4 dst: 30.1.1.1
IPv4 src: 10.0.0.1
TCP dst: 80
TCP src: 10000
IPv4 dst: 10.0.0.1
IPv4 src: 30.1.1.1
TCP dst: 10000
TCP src: 80
As shown in Figure 120, the packet forwarding process in DS-Lite is as follows:
a. Upon receiving a packet from the private IPv4 network, the B4 router adds an IPv6 header
to the packet and sends the IPv6 packet to the AFTR through the tunnel.
b. The AFTR performs the following operations:
− Removes the IPv6 header from the tunneled packet.
− Assigns a tunnel ID for the B4 router.
− Records the mapping between the IPv6 address of the B4 router (the source IPv6
address of the packet), and the tunnel ID.
c. After de-encapsulation, the AFTR translates the source private IPv4 address of the packet
into a public IPv4 address and sends the packet to the destination IPv4 host. The AFTR also
maps the NAT entries to the tunnel ID so that IPv4 networks connected to different B4
routers can use the same address space.
d. Upon receiving the response packet from the public network, the AFTR translates the
destination public IPv4 address into the private IPv4 address. The AFTR performs the
following operations:
− Looks up the IPv6 address-tunnel ID mapping to obtain the IP address of the B4 router.
− Uses the address as the destination address of the encapsulated IPv6 packet.
− Forwards the packet to the B4 router.
Figure 120 shows an example of PAT translation for dynamic NAT. Typically, dynamic NAT is
used. When you use static NAT for DS-Lite tunneling, make sure the IP addresses of private
IPv4 networks connected to different B4 routers do not overlap. For more information about
NAT, see "Configuring
1::1/64
IPv6 network
DS-Lite tunnel
B4
IPv6 dst: 2::1
IPv6 src: 1::1
IPv4 dst: 30.1.1.1
Adds an IPv6
IPv4 src: 10.0.0.1
header
TCP dst: 80
TCP src: 10000
Removes
the IPv6
header
NAT."
290
2::1/64 20.1.1.1/24
AFTR
Removes the
IPv6 header
and performs
NAT
IPv6 dst: 1::1
IPv6 src: 2::1
Performs NAT
IPv4 dst: 10.0.0.1
and adds an
IPv4 src: 30.1.1.1
IPv6 header
TCP dst: 10000
TCP src: 80
30.1.1.1/24
IPv4 network
IPv4 host
IPv4 dst: 30.1.1.1
IPv4 src: 20.1.1.1
TCP dst: 80
TCP src: 5000
IPv4 dst: 20.1.1.1
IPv4 src: 30.1.1.1
TCP dst: 5000
TCP src: 80