Note: This is part one of two; the second part will be posted next week.
No matter what your position in IT might be, you're probably pretty darn familiar with IPv4. You can't configure the first thing on a network today without at least having some basic idea how subnet masks, default gateways, and DNS allow the network to function. If you're tasked with day-to-day management of a larger network, you may be very familiar with a whole slew of deeper info, such as how to set up DHCP to autonumber workstations, perform more complex subnetting, and configure dynamic routing protocols.
For better or for worse, everything you've learned about IP throughout your career is about to change.
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The IANA issued its last /8 block of IPv4 addresses earlier this month. The Regional Internet Registries are on pace to run out of smaller blocks to assign to ISPs and corporations within a year or so. Many ISPs have done a good job planning ahead and have a lot of space on hand, but it can't last forever. It's not an issue of whether IPv4 address space exhaustion will force you to get on the IPv6 bandwagon, but when.