R3303-HP HSR6800 Routers Layer 3 - IP Services Configuration Guide

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The encapsulation and de-encapsulation processes illustrated in Figure 97 are described as follows:
• Encapsulation:
a. Upon receiving a IPv4 packet, Device A delivers it to the IPv4 protocol stack.
b. The IPv4 protocol stack uses the destination address of the packet to determine the output
interface. If the output interface is the tunnel interface, the IPv4 protocol stack delivers the
packet to the tunnel interface.
c. The tunnel interface adds an IPv6 header to the original IPv4 packet and delivers the packet to
the IPv6 protocol stack.
d. The IPv6 protocol stack uses the destination IPv6 address of the packet to look up the routing
table and sends it out.
• De-encapsulation:
e. Upon receiving the IPv6 packet from the attached IPv6 network, Device B delivers the packet
to the IPv6 protocol stack to examine the protocol type encapsulated in the data portion of the
packet.
f. If the protocol type is IPv4, the IPv6 protocol stack delivers the packet to the tunneling module.
g. The tunneling module removes the IPv6 header and delivers the remaining IPv4 packet to the
IPv4 protocol stack.
h. The IPv4 protocol stack forwards the IPv4 packet.
IPv4 over IPv6 manual tunnel
In this tunnel mode, you must manually configure the source and destination IPv6 addresses for the tunnel.
An IPv4 over IPv6 manual tunnel is a point-to-point virtual link.
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 98 Principle of IPv6 over IPv6 tunneling
Figure 98 shows the encapsulation and de-encapsulation processes:
• Encapsulation
a. After receiving the an IPv6 packet, Device A submits it to the IPv6 protocol stack.