1. OverviewΒΆ

An ISP having already migrated to an IPv6-only core network still needs to reach the IPv4 world while dealing with IPv4 depletion. This can be achieved using CG-NAT. This specific usage, called NAT64, involves a DNS64 server that returns custom-built IPv6 addresses for IPv4-only hosts, using a well-known prefix reserved for this usage. The vRouter can be used in front of an existing DNS name server to fulfill this function.

CG-NAT, also known as Large Scale NAT, is a highly scalable NAT placed in the ISP core network, between the customer premises equipment (CPE) and the Internet.

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In NAT64, there are three networks:

  • A private IPv4 network within the user network (behind the CPE),

  • A private IPv6 network for the user to provider links (between the CPE and the vRouter), using the well-known prefix,

  • A public IPv4 network on the outside of the vRouter.