I wanted to give a starter course on networking, so here it is. It is a little dry, and I am going to go over it.
IP (internet Protocol) networking is the 3rd layer of a 7 layer system known as the ISO model.
Every Ethernet connection on the internet must have a unique ip address that consists of 4 sets of 3 numbers. Each individual set can reach a max of 254.
these are valid IP addresses:
4.2.2.2
173.34.133.45
245.249.8.244
10.0.0.1
192.168.1.1
The IP information that is required to make a connection to the internet are as follows:
IP address
subnet mask
default router or gateway
Domain names server(s) (DNS)
The subnet mask determines how large or small the relevant network is. 99% of all Local Area Networks (LAN’) that we will work with will have a subnet mask of 255.255.255.0, or what is referred to as a “class C” A “class B” network will have a subnet mask of 255.255.0.0 and have the ability to contain 254×254 machines. A “class A” network will have a subnet mask of 255.0.0.0
What a subnet mask of 255.255.255.0 means is that their can be a max of 254 machines on that specific network.
Default router or Gateway, is the address of the ethernet adapter that the machine has to go through in order to get out to the internet. 90% of the time the default router is the same as the IP address, but with a 1 in the last octet.
example
ip address 192.168.1.100
subnetmask 255.255.255.0
gateway 192.168.1.1
The DNS servers tell the computer what the IP address of a website is. For example a DNS server will tell you that google.com is at IP address 64.233.187.99. So with out the DNS servers set properly the computer will not be able to resolve domain names into IP addresses.
Here is an example of an internet routable IP address, subnet mask, gateway, and DNS for a machine that is currently on the internet.
ip addy: 216.174.121.58
gateway: 216.174.121.57
subnet: 255.255.255.248
dns1: 12.127.16.67
dns2: 12.127.17.71
Most likely all of the machines that we deal with will have what are called NON-ROUTABLE IP addresses. Or address that are not available to from the internet. These address are what are used in almost all Local Area Networks (LAN’s). The following is a list of non-routable IP addresses (where ‘x’ is any number up to 255):
10.x.x.x
192.168.x.x
127.x.x.x
So when ever you see an IP address that is like the ones listed above you will know you are dealing with a LAN.
When dealing with LAN’s and NON-ROUTABLE IP’s their is a protocol called Network Address Translation (NAT). This translates a single internet routable IP address into a shared connection for those within the LAN to connect through in order to access the internet.
These addresses are assigned automatically to local computers by a service called Dynamic Host Configuration Protocol (DHCP). This assigns an IP address, a subnet mask, a gateway, and DNS servers to a machines that are on the LAN and make a request as a lease for a specified amount of time between a few hours and a week or more.
As an example, The average linksys wireless router or Airport Base Station performs all of these function right out of the box, but as they malfunction it is important to know how to work around them.