Appendix
Appendix: Network Basics
Networks and Routing Basics
ThischapterprovidesanoverviewofIPnetworks,routing,andfirewalls.Thisisbynomeans a complete overview! If you are looking for more information, you can use your favorite search engine to find information on the internet. Suffice to say, there is plenty.
Basic Router Concepts
Even though the amount of bandwidth in your local area network (LAN) can be provided easily and relatively inexpensively, the price of the connection to the internet is much higher. Because of this expense, Internet access is usually provided by a
link such as a cable or DSL modem. To use this WAN link efficiently, a mechanism must be in EN place for selecting and transmitting only the data traffic meant for the Internet. The function of
selecting and forwarding this data is performed by a router.
What is a Router?
A router splits the information meant for your network and meant for other networks, so the available bandwidth is used efficiently. The router sends data based on network layer information in the data and on routing tables maintained by the router. The rout- ing tables are built by gathering and exchanging information with other routers in the network. The router builds up a logical picture of the overall network. Using this infor- mation, the router chooses the best path for forwarding network traffic. Routers vary in performance and scale, number of routing protocols supported, and types of physical WAN connection they support.
Routing Information Protocol
One of the protocols used by a router to build and maintain a picture of the network is the Routing Information Protocol (RIP). Using RIP, routers periodically update one another and check for changes to add to the routing table.
IP Addresses and the Internet
For a computer to communicate with other computers and Web servers on the Internet, it must have a unique IP address. An IP address (IP stands for Internet Protocol) is a unique number that identifies the location of your computer on a network.
Basically, it works like your street address - as a way to find out exactly where you are and deliver information to you. The IP address is written as 4 numbers between 0 and 255, such as "192.168.0.12".
This serves the same basic function as a street address. It helps you find out where you currently are, while also providing other information. The IP address consists of four numbers between 0 and 255 (e.g., 192.168.0.12).