I have a stable network but expect growth in my access network

This case is one where service providers are in the process of migrating from an older access technology to a newer one. For example, they may be moving from DSL to fiber, and thus have two access networks that are growing at different rates. The investment to deploy IPv6 natively may be more difficult to justify in the legacy environment. Still, IPv4 address depletion is seen as an impending threat.

NAT444 is an architecture that enables these providers to deal with address shortages at the lowest cost. The advantage of NAT444 is that there is no change required to CPE equipment and no upgrade to IPv6 in any part of the network. The cost of introducing NAT444 includes the cost of the CGNAT device in the service provider network, and the operational cost of configuring, testing, and managing it.

As illustrated in this figure, this case will typically include NAT at the CPE (access device). The change at the CPE is that the translated outside address is also a private IPv4 address. The second NAT is performed in the service provider infrastructure, and private addresses are translated to public addresses on the outside of the CGNAT device.

This figure also shows the way traffic separation for legacy and new customers is performed via MPLS. With MPLS, legacy customers with global IPv4 addresses can bypass the CGNAT, and customers with private IPv4 addresses can be directed to the CGNAT device in the provider infrastructure.

In this case, 6rd (RFC 5969) can be a complementary technology that can be deployed in order to provide a local solution to deploy IPv6 with customers that have an upgraded CPE.

To know more about the tools that support this scenario download the paper:
Tools and Strategies for Coping With IPv4 Address Depletion [ 1 MB ]