“I’ve written previously that as we make the slow – and long
overdue – transition from IPv4 to IPv6, we will soon be stuck with
an awkward interim period in which the only new globally routable
addresses we can get are IPv6, but most public content we want to
reach is still IPv4. Large Scale NAT (LSN, also known as Carrier
Grade NAT or CGN) is an essential tool for stretching a service
provider’s public IPv4 address space during this transitional
period.“I’ve yet to work an IPv6 project involving LSN in which someone
does not eventually, with great hope in his eyes, say, “If LSN
extends the life of our IPv4 space, why are we going to the pain
and expense of deploying IPv6? Can’t we just deploy LSN and forget
about IPv6 for now? Perhaps until I retire?”“A first look LSN does indeed seem to promise an extended
lifetime for IPv4. Could it even mean that the Internet never has
to transition to IPv6?“This article looks beyond the mechanisms of LSN itself to
examine the implications of LSN in a practical network, and why
this useful technology should never be viewed as anything other
than an interim solution.”