IP addresses

Each server or client on a TCP/IP internet is identified by a numeric IP (Internet Protocol) address. The two types of IP address are the IPv4 (IP version 4) address and the IPv6 (IP version 6) address.

IP addresses are managed and allocated to users by the Internet Assigned Numbers Authority (IANA) and its delegates. The internet address specifies both the network and the individual host. This specification varies with the size of the network.

IPv6 addresses

IPv6 addresses are 128-bit addresses, usually expressed in hexadecimal notation: 
IP address in hexadecimal notation :   '000100220333444400000000abc0def0'x
Halfword 0:  0001 hexadecimal
Halfword 1:  0022 hexadecimal
Halfword 2:  0333 hexadecimal
Halfword 3:  4444 hexadecimal
Halfword 4:  0000 hexadecimal
Halfword 5:  0000 hexadecimal
Halfword 6:  abc0 hexadecimal
Halfword 7:  def0 hexadecimal
IP address in colon hexadecimal notation: 1:22:333:4444::abc0:def0

IP address in hexadecimal notation :   '00000000000000000000ffff01020304'x
Halfword 0:  0000 hexadecimal
Halfword 1:  0000 hexadecimal
Halfword 2:  0000 hexadecimal
Halfword 3:  0000 hexadecimal
Halfword 4:  0000 hexadecimal
Halfword 5:  ffff hexadecimal
Halfword 6:  0102 hexadecimal
Halfword 7:  0304 hexadecimal
IP address in colon hexadecimal notation: ::ffff:1.2.3.4 or ::ffff:0102:0304
The address consists of eight halfword fields. Zeros are treated in the following ways in the address output:
  • If a field contains leading zeros, they are ignored; for example, 0001 is represented as 1
  • If one or more consecutive fields in the address contain the value 0000, these fields are expressed using the notation ::

    For example, 000000000000ffff is represented as ::ffff

    The :: substitution is used once only in an address, to avoid confusion in calculating how many fields were substituted.

IPv4 addresses

IPv4 addresses are 32-bit addresses, usually expressed in dotted decimal notation: 
IP address in hexadecimal notation :   '817EB263'x
Byte 0:  81 hexadecimal = 129 decimal
Byte 1:  7E hexadecimal = 126 decimal
Byte 2:  B2 hexadecimal = 178 decimal
Byte 3:  63 hexadecimal =  99 decimal
IP address in dotted decimal notation: 129.126.178.99
In this example, 129.126 specifies the network and 178.99 specifies the host on that network.