1. What do you need to know about addresses?
You probably know what an IP address is: a number that identifies that device on the network. But what else do you need to know? IP addresses are made up of 32 bits (IPv4 addresses, that is). We normally think of an IP address as something like 220.127.116.11, but really this can be translated into eight binary bits. Each set of binary bits can represent only the numbers zero through 255. That is why your IP addresses can range only from 0.0.0.0 to 255.255.255.255.
By the way, the IP address 255.255.255.255 is called the "all ones" network because in binary it is represented by 32 numeral ones (1s). The all ones address is used to send a packet to all devices on all networks (as long as it isn''''t stopped by a router first).
Traditionally, IP addresses were broken up into classes, but those classes aren''''t used much any more unless you are taking a certification exam. We will learn more about classes below.
Most importantly, IP addresses must be unique on your network. If two devices have the exact same IP address, you have an IP address conflict. When that happens, either device or both devices will not work on the network. Commonly, is used to dynamically allocate IP addresses in hopes of preventing address duplication and easing the administrative burden of static IP addressing.
2. What is a subnet mask?
A subnet mask is
Of special note when looking at the number of hosts in a network is this: The first IP address in a network is the network address and the last IP address is always the broadcast address. That''''s why I couldn''''t use IP address 18.104.22.168 and IP address 22.214.171.124. These are special, reserved addresses, but some computers will allow you to use the network address as a real computer address.
"Subnetting" is breaking up a single network into smaller networks. To do this, you add more bits (more numbers) to the subnet mask. Traditionally, we are used to seeing subnet masks that look like 255.0.0.0, 255.255.0.0, or 255.255.255.0. However, a subnet mask might also look like 255.255.128.0 or 255.255.255.224. In both of these cases, it is obvious that the network has been subnetted to break a single network into smaller networks.
Tomorrow: Classless vs. Classful IP addressing