The last available IPv4 addresses have been allocated, which means we all need to start learning about and using IPv6!

IP addresses are a set of numbers that uniquely identify a host on the internet. IPv4 addresses are composed of four separate 8-bit numbers (for a total of 32 bits), from 0-255, written as As an example, you can run the nslookup command on a domain name, and find the IP address. Many websites have multiple IP addresses, for redundancy. Running an nslookup on shows us an IP addresses of, along with a few more for redundancy.

Every computer that is connected to the internet needs an IP address. Using NAT we can decrease the number of necessary IPv4 addresses, by creating private IPv4 address segments for home and small networks, but that only delayed the exhaustion of IPv4 addresses. The only way to solve the problem is with new, bigger IPv6 addresses.

IPv6 addresses are composed of eight separate 16-bit numbers (for a total of 128 bits), from 0-ffff, written as 1111:2222:3333:4444:5555:6666:7777:8888. IPv6 also allows for a single consecutive string of zero’s to be omitted, and for leading zero’s in a 16-bit section to be omitted, making the address easier to write. Google’s ipv6 server,, has an IPv6 address of 2001:4860:800f::68. Notice the two consecutive colons? Between those colons are actually a bunch of zero’s! So Google’s IPv6 address would actually look like 2001:4860:800f:0000:0000:0000:0000:0068.

On the left are some statistics from Hurricane Electric about IPv4 and IPv6 usage. Hurricane Electric has a neat and fun IPv6 certification program to help you learn all about IPv6. They also provide IPv6 tunnels so you can get access to IPv6 if your ISP isn’t providing IPv6 access yet. Best of all it’s FREE! isn’t quite IPv6 ready yet, but we will be soon, and we’ll show you how to set up a tunnel and complete the IPv6 certification program. SophieDogg is already an IPv6 Sage at Hurricane Electric, and you can be too! Arf!

Some more fun facts about IPv4 and IPv6:

  • IPv4 has a total of 232 unique possible addresses (4,294,967,296)
  • IPv6 has a total of 2128 unique possible addresses (340,282,366,920,938,463,463,374,607,431,768,211,456)
  • IP Addresses are often written using Classless Inter-Domain Routing (CIDR) notation
  • An address written as uses CIDR to specify that the first 8 bits are the routing prefix. This is also sometimes written as
  • An address written as specifies that the first 24 bits are the routing prefix. This can also be written as
  • An IPv6 address can also be written using CIDR. 2000:fe6::/32 specifies that the first 32 bits are the routing prefix.