Ken's Korner
The Devil made me do it!

IP ADDRESSING, THE BASICS

Structure of the IP Address
An internet consists of several individual Networks connected by bridges or routers. Each individual Network (also called a physical network) consists of a group of Hosts (computers, etc.) that are "directly connected" to each other via a common cable or common hub (or group of hubs).
It's important to clarify what is meant by "directly connected". This involves cable ports and hubs only. It does not include bridges, routers or the I/O bus. For example, 2 Nics in the same computer are NOT "directly connected" and therefore exist on separate networks, even though they may be bridged or routed together by the computer's operating system or other software. Similarly, Hosts whose only common connection is a bridge or router, are considered to be on separate networks. Like the 2 Nic example, each cable port of the bridge or router are not "directly connected" and therefore exist on separate networks.

Network Addressing and Host Addressing

Each Network and each Host requires its own identifying number, its IP Address.

The Network Address is a unique number, consisting of a special pattern, that is assigned to each Network (physical network). These addresses may not be used for Host addresses. Example:

(notice the trailing zeros in each example)

NOTE: If your network is connected to the outside world, you must obtain your primary Network Address from interNIC to avoid duplicating and conflicting with the IP addresses of other organizations. If your network is isolated, you may use any valid IP Network address.

The Host Address is a unique number assigned to each individual device (network card, router, etc.). It will be a sub-set of the Network Address to which it is physically connected. As mentioned before, it is important to note that Network Addresses may NOT be used for Host addresses. Example:

Some sample text that has no other purpose other than to show how text wraps around an object. Cool huh!

Some sample text that has no other purpose other than to show how text wraps around an object. Cool huh!

Some sample text that has no other purpose other than to show how text wraps around an object. Cool huh!

Some sample text that has no other purpose other than to show how text wraps around an object. Cool huh!

What do you do if you need more than one IP Network. For example, if you have 2 network cards in the same server, they're on different physical networks and therefore need to be assigned different network numbers. Without different network numbers, the server doesn't know which adapter to communicate through.

One solution would be to request another Primary Network Number from interNIC, but that's not practical or necessary. Instead, you can use some of your available Host bits to define additional networks. Recall the class B example where the "n" bits are reserved for Network addressing and the "h" bits are available for Host addressing: