an ip address is a long binary number, made of ones and zeros. an ipv4 address is 32 binary digits (or bits) long. an ipv6 is 128 bits long, allowing many more ip addresses to be used. ip addresses are usually written in human-readable form, where 8 bits are grouped into one octet. ipv4 addresses are usually written as a group of four numbers. each number can take a value from 0 to 255. ipv6 addresses are written as a group of eight hexadecimal numbers. many ipv6 addresses contain many zeroes. there are special rules which say that in certain cases, these zeroes do not need to be written.