Ipv4 Over Ipv6 Tunneling - HP 6125XLG Configuration Manual

Encapsulation:
•
a. Device A receives an IP packet from an IPv4 host and submits it to the IP protocol stack.
b. The IPv4 protocol stack determines how to forward the packet according to the destination
address in the IP header. If the packet is destined for the IPv4 host connected to Device B,
Device A delivers the packet to the tunnel interface.
c. The tunnel interface adds a new IPv4 header to the IPv4 packet and submits it to the IP protocol
stack. In the new header, the source IP address specifies the tunnel source, and the destination
IP address specifies the tunnel destination. The IP protocol stack uses the destination IP address
of the new IP header to look up the routing table, and then sends the packet out.
• De-encapsulation:
d. After receiving the packet, Device B delivers it to the IP protocol stack.
e. If the protocol number is 4 (indicating an IPv4 packet is encapsulated within the packet), the IP
protocol stack delivers the packet to the tunnel module for de-encapsulation.
f. The tunnel module de-encapsulates the IP packet and sends it back to the IP protocol stack.
g. The protocol stack forwards the de-encapsulated packet.

IPv4 over IPv6 tunneling

IPv4 over IPv6 tunneling enables isolated IPv4 networks to communicate with each other over an IPv6
network.
In this tunnel mode, you must manually configure the source and destination IPv6 addresses for the tunnel.
An IPv4 over IPv6 tunnel is a point-to-point virtual link.
Figure 71 Principle of IPv4 over IPv6 tunneling
The encapsulation and de-encapsulation processes illustrated in
Encapsulation:
•
a. Upon receiving an 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 egress
interface. If the egress 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 then sends it out.
Figure 71
160
are described as follows: