R0106-HP MSR Router Series Layer 3 - IP Services Configuration Guide(V7)

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− 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 109 shows an exam
ple 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."
IPv6 over IPv6 tunneling
IPv6 over IPv6 tunneling (RFC 2473) enables isolated IPv6 networks to communicate with each other over
another IPv6 network. For example, two isolated IPv6 networks that do not want to show their addresses
to the Internet can use an IPv6 over IPv6 tunnel to communicate with each other.
Figure 110 Principle of IPv6 over IPv6 tunneling
Figure 110 shows the encapsulation and de-encapsulation processes.
• Encapsulation:
a. After receiving an IPv6 packet, Device A submits it to the IPv6 protocol stack.
b. The IPv6 protocol stack uses the destination IPv6 address of the packet to find the egress
interface. If the egress interface is the tunnel interface, the stack delivers it to the tunnel
interface.
c. After receiving the packet, the tunnel interface adds an IPv6 header to it and submits it to the
IPv6 protocol stack.
d. The IPv6 protocol stack forwards the packet according to its destination IPv6 address.
• De-encapsulation:
e. Upon receiving the IPv6 packet, Device B delivers it to the IPv6 protocol stack.
f. The IPv6 protocol stack checks the protocol type of the data portion encapsulated in the IPv6
packet. If the encapsulation protocol is IPv6, the stack delivers the packet to the tunnel module.
g. The tunnel module de-encapsulates the packet and sends it back to the IPv6 protocol stack.
h. The IPv6 protocol stack forwards the IPv6 packet.
Protocols and standards
• RFC 1853, IP in IP Tunneling
• RFC 2473, Generic Packet Tunneling in IPv6 Specification