Packet Flow Through the 6to4 Tunnel

This section describes the path of packets from a host at one 6to4 site to a host in a remote 6to4 site. The next scenario uses the topology that is shown in Figure 4–3 as its example. Moreover, the scenario assumes that the 6to4 routers and 6to4 hosts are already configured.

1. A host on Subnet 1 of 6to4 Site A sends a transmission, with a host at 6to4 Site B as the destination. Each packet header in the flow has a source 6to4–derived address and destination 6to4– derived address.

2. 6to4 Router A receives the outgoing packets and creates a tunnel over an IPv4 network to 6to4 Site B.

3. Site A's router encapsulates each 6to4 packet into an IPv4 header. Then the router uses standard IPv4 routing procedures to forward the packet over the IPv4 network.

4. Any IPv4 routers that the packets encounter use the packets' destination IPv4 address for forwarding. This address is the globally unique IPv4 address of the interface on Router B, which also serves as the 6to4 pseudo-interface.

5. Packets from Site A arrive at Router B, which decapsulates the IPv6 packets from the IPv4 header.

6. Router B then uses the destination address in the IPv6 packet to forward the packets to the recipient host at Site B.