Last month, I ran into quite a snag when trying to install a second iteration of WordPress MU on my server. I currently run a copy for this site and some others I manage, but I also have a few other clients on my server and one of them would like to also run multiple sites. I quickly found out exactly why you can’t run multiple instances of WordPress MU without a few caveats.

The caveat to be explored here is one that affects many areas of the Internet and its users. IPv4 is the fourth revision of the Internet Protocol. In layman’s terms, it’s the protocol that provides you with the IP address allowing you to get on the Internet. You may have seen them on your computer or device: XXX.XXX.XXX.XXX

Each octet can have 255 bits in it, meaning the whole IP address range is 0.0.0.0 to 255.255.255.255 and after removing a few reserved address blocks, you end up with about 4.3 billion combinations. In the original concept of the Internet, reaching this ceiling was thought to be impossible since the Internet was never to be used by the mass public. In order for a device to be on the Internet, it needs to have its own IP address.

In the beginning of the public Internet, large blocks of IP addresses were given to the phone companies to issue out to their customers based on various needs. At this time, if a computer network contained a thousand computers, 1,000 unique IP addresses were needed. This caused a lot of corporations to lease very large amounts of IP addresses. All that changed when Network Address Translation (NAT) was created. NAT allowed a network to use one public IP address for the entire network and a device such as a router to issue out individual private IP addresses to each device connected to it.

Confused yet?! It’s ok…that’s about as deep as I want to get in the definition of IP. Where I’m going with this is that no more IP addresses are available because the last 5 blocks were allocated to the 5 regional Internet registries (RIRs) on February 3, 2011. This doesn’t mean that all are being used, but they are at least in the hands of those responsible for leasing them to customers.

With that said, IPv4 is essentially dying, if not already dead. Our only hope now is the release of IPv6 which would allow for 340 undecillion IP address, or about 5 x 10²⁸ addresses for each of the 6.8 billion people alive on the earth today.