33 IPV6 Tunnel Configuration
33.1 Overview
The IPv6 is designed to inherit and replace the IPv4. However, the evolution from the IPv4 to
the IPv6 is a gradual process. Therefore, before the IPv6 completely replaces the IPv4, it is
inevitable that these two protocols coexist for a period. At the beginning of this transition
stage, IPv4 networks are still main networks. IPv6 networks are similar to isolated islands in
IPv4 networks. The problems about transition can be divided into the following two types:
1. The problem about the communication between isolated IPv6 networks via IPv4
networks
2. The problem about the communication between IPv6 networks and IPv4 networks
This article discusses the tunnel technology that is used to solve problem 1. The solution to
problem2 is NAT-PT (Network Address Translation-Protocol Translation), which is not
covered in this article.
The IPv6 tunnel technology encapsulates IPv6 packets in IPv4 packets. In this way, IPv6
protocol packets can communicate with each other via IPv4 networks. Therefore, with the
IPv6 tunnel technology, isolated IPv6 networks can communicate with each other via
existing IPv4 networks, avoiding any modification and upgrade of existing IPv4 networks. An
IPv6 tunnel can be configured between Area Border Routers or between an Area Border
Router and the host. However, all the nodes at the two ends of the tunnel must support the
IPv4 and IPv6 protocol stacks. At present, our company supports the following tunnel
technologies: