IPv6 uses a 128-bit address, as opposed to the IPv4 32-bit address. Unlike IPv4 addresses, which use the dotted-decimal format, with each octet assigned a decimal value from 0 to 255, IPv6 addresses use the colon-hexadecimal format X:X:X:X:X:X:X:X, where each X is a 16-bit section of the 128-bit address. For example:
2001:0db8:0000:0000:0000:0000:0000:0000
Leading zeros must be omitted from each block in the address. A series of zeros can be replaced with a double colon. For example:
2001:db8::
The double colon can only be used one time in an address.
The IPv6 prefix is the part of the IPv6 address that represents the network identifier, which appears at the beginning of the address. The IPv6 prefix length, which begins with a forward slash (/), shows how many bits of the address make up the network identifier. For example, the address 2001:db8:8086:6502::1/64 means that the first 64 bits of the address represent the network identifier; the remaining 64 bits represent the node identifier.
IPv6 addresses and prefixes are displayed according to RFC 5952, A Recommendation for IPv6 Address Text Representation.