
Chapter 5 • IPv6 Transition Issues 77
will continue to be useful for connectivity across IPv4-only backbones and
other holdout networks.
The other prong of the strategy is the dual-stack approach, in which hosts
and routers run IPv4 and IPv6 stacks on the same network interfaces. This
way, a dual-stack node can accept and transmit both IPv4 and IPv6 packets,
so the two protocols can coexist on the same networks.
5.2 The IPv6 Protocol Tunneling Approach
Tunneling requires that an IPv6 node at one end of the tunnel be capable of
transmitting IPv4 packets (dual-stack node, see next section) and that there
be another dual-stack node at the other end of