IPv4 Address

32-bit
2^32 4,294,967,296 possible addresses under IPv4 - now ran out.
Can be referred to in binary, hex, octal, dotted decimal and decimal.
- 10.10.10.10 (Dotted Decimal)
- 00001010.00001010.00001010.00001010 (Decimal)
Structured to aid routing
- Network Number (globally unique, find correct network)
- Host Number (locally unique, find correct node)
- ^ outdated
No. bits allocated to each part varies depending on how many host numbers needed (see: subnetting, netmask)
Nodes with the same network number are on same network, and vice versa.
Network number tells transmitter which case is true.

Classful IP Addresses

A and B have large address ranges.
Either need multiple network numbers, or use subnets to pretend you have multiple network numbers
One LAN per building, big network likely to be split into smaller networks. (Subnets)