
Chapter 5 • IPv6 Transition Issues 83
Figure 5–3: Dual-stack systems can interoperate with IPv4 and IPv6 nodes.
no IPv6 routing path from network A to network C. The router linking
networks A and M supports only IPv4 and thus cannot forward any IPv6
packets to network C (via network M).
Dual-stack nodes that can perform tunneling add the ability to interoperate
over IPv4 networks without any additional IPv6 routers. Tunneling IPv6
over IPv4 can change the connectivity picture in Figure 5–3. For example, if
node D is able to tunnel IPv6 over IPv4, then it can use its local IPv4 router
to forward packets to network C. If the nodes both support automatic ...