Ipv4 Over Ipv6 Tunneling - HP 6125XLG Layer 3-Ip Services Configuration Manual

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 adds an IPv6 header to IPv4 packets so that IPv4 packets can pass an IPv6
network through a tunnel to realize interworking between isolated IPv4 networks.
Figure 85 IPv4 over IPv6 tunnel
Packets traveling through a tunnel undergo encapsulation and de-encapsulation, as shown 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.
• 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.
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Figure 85.