The final, pesky challenge many organizations worry about is how to deal with their legacy applications -- those backend behemoths that will never support IPv6 directly. In fact, these systems should be the least of your worries. It will be nearly a decade before IPv6 takes full center stage from IPv4. By then, you might have replaced these systems. If not, you will have done everything necessary to make your infrastructure hum along beautifully on IPv6. For the few remaining IPv4 stragglers, proxying traffic will still be a legitimate solution, so get ready to circle back to Phase I.
After that, go clean your room.
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