IPv4 over IPv6 tunneling

IPv4 over IPv6 tunneling adds an IPv6 header to IPv4 packets so that the IPv4 packets can traverse an IPv6 network and reach another IPv4 network.

The encapsulation and de-encapsulation processes illustrated in Figure 86 are described as follows:

• Encapsulation

  1. Upon receiving a packet from the attached IPv4 network, Device A examines the destination address of the packet and determines the outgoing interface.

  2. If the packet is destined for the IPv4 network attached to Device B, Device A delivers the packet to the tunnel interface pointed to Device B.

  3. The tunnel interface adds an IPv6 header to the original IPv4 packet and delivers the packet to the IPv6 protocol stack for forwarding.

• De-encapsulation

  1. Upon receiving a 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.

  2. If the protocol type is IPv4, the IPv6 protocol stack delivers the packet to the tunneling module.

  3. The tunneling module removes the IPv6 header and delivers the remaining IPv4 packet to the IPv4 protocol stack for subsequent forwarding.