H3C MSR 2600 Configuration Manual page 257

Figure 100 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
Figure 100 shows a packet passing through a DS-Lite tunnel between IPv4 networks.
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 removes the IPv6 header of the tunneled packet, assigns a tunnel ID for the B4 router,
and 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 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, and forwards the packet to the B4 router.
Figure 100 shows an example of PAT translation for dynamic NAT. DS-Lite tunneling also supports
static NAT and NO-PAT. Typically, dynamic NAT is used. When you use static NAT for DS-Lite
tunneling, make sure the IP addresses of private IPv4 networks connecting to different B4 routers
do not overlap. For more information about NAT, see "Configuring NAT."
1::1/64
IPv6 network
DS-Lite tunnel
B4
IPv6 dst: 2::1
IPv6 src: 1::1
IPv4 dst: 30.1.1.1
Adds the
IPv4 src: 10.0.0.1
IPv6 header
TCP dst: 80
TCP src: 10000
IPv4 dst: 10.0.0.1
IPv4 src: 30.1.1.1
TCP dst: 10000
Removes the
IPv6 header
242
2::1/64 20.1.1.1/24
IPv4 network
AFTR
Removes the
IPv6 header and
performs NAT
IPv6 dst: 1::1
IPv6 src: 2::1
Performs NAT
and adds the
IPv6 header
TCP src: 80
30.1.1.1/24
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