2(2)T and later
Strategies for Implementing IPv6
The transition from IPv4 does not require upgrades on all nodes at the same time. Many
transition mechanisms enable smooth integration of IPv4 and IPv6. Other mechanisms that
allow IPv4 nodes to communicate with IPv6 nodes are available. All of these mechanisms
are applied to different situations. Figure 7-13 shows how IPv6 hosts may have to travel
across IPv4 networks during this transition.
Figure 7-13 IPv4-to-IPv6 Transition
The three most common techniques to transition from IPv4 to IPv6 are as follows:
?– Dual stack: Dual stack is an integration method in which a node has implementation
and connectivity to both an IPv4 and IPv6 network. As a result, the node and its
corresponding routers have two protocol stacks.
?– Tunneling: Several tunneling techniques are available:
??” Manual IPv6-over-IPv4 tunneling: An integration method in which an
IPv6 packet is encapsulated within the IPv4 protocol. This method
requires dual-stack routers.
IPv6
Host
IPv6
Host
6to4
Router
6to4
Router
IPv6
Network
IPv4
Network
IPv6 Traffic
IPv6
Network A B
284 Chapter 7: Managing Address Spaces with NAT and IPv6
??” Dynamic 6to4 tunneling: A method that automatically establishes the
connection of IPv6 islands through an IPv4 network, typically the
Internet.
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