IPv4-to-IPv6 Transition

Implementing IPv6 requires a transition mechanism to allow interoperability between IPv6 nodes (both routers and hosts) and IPv4 nodes. The transition mechanism is the key factor in the successful deployment of IPv6. Because millions of IPv4 nodes already exist, upgrading every node to IPv6 at the same time is not feasible.

As a result, transition from IPv4 to IPv6 happens gradually, allowing nodes to be upgraded independently and without disruption to other nodes. While a gradual upgrade occurs, compatibility between IPv6 and IPv4 nodes becomes a requirement. Otherwise, an IPv6 node would not be able to communicate with an IPv4 node.

Transition mechanisms allow IPv6 and IPv4 nodes to coexist together in the same network, and make gradual upgrading possible. Two transition mechanisms are supported by the JUNOS Internet software:

• Dual IP layer operation—Allows a node to support both IPv6 and IPv4 Internet protocols. This mechanism is also known as dual stack.
• Configured tunnels—Allows IPv6 packets to be encapsulated into IPv4 headers and sent across an IPv4 infrastructure.