Wireless Router - Static and Dynamic IP Rev. 2

Note: This is a revision of an article that i have written before. It seems to be a pretty popular article. I would really like for people to comment on whether they liked it or didn't like it. Any recommendations on how to make it better.

So i am pretty sure many of you have encountered this problem before. You have multiple computers in your house and you want all the computers to be able to access the internet at the same time without signing up for additional internet service. The answer to this problem is to get a router.

A router basically takes one ip address and then it lets you share that one address among multiple computers.

This way instead of just one computer been able to connect to the internet, multiple computers can share that one internet connection. To help you understand what a router is, let's say that the one ip address given to you by your provider is similar to your university mailing address. But the university has different building within it. So once a mail arrives at the university, the mail sorter has to sort out the mail by the building name and then deliver it to the proper recipient. This is exactly what the router does, it sorts the traffic for the different computers and delivers them to the correct computer.

This setup works fine for a regular user. But you might encounter a problem if you want to run a server or if you wanna be able to use bit torrent. The reason you would encounter a problem is because these services(such as webserver) works by an outside user trying to access your system without specifying who they are trying to communicate with. This would relate to the case where someone sends a letter which does not contain the building name. This would make it impossible for the mail sorter to decide who this mail is addressed to. The way to work around this problem is by specifically asking the router to forward any requests that comes from X to a particular computer. In the analogy case, it means you would tell the mail sorter that any mail from this person should always be delivered to me even when its missing the building name.

The only problem with the above case is that with most routers, the addresses are handed out dynamically.What this means is whenever a computer is turned on, it requests for a new address from the router. So whats wrong with that? Well, the computers on the network would not be guaranteed to have the same address each and every time. Imagine the university changing the name of the buildings on campus each day, this would make it impossible for the mail sorter to know which building to deliver the mail.

In order to avoid any confusion, we will configure it so that each computer will always get the same address. This can be achieved by configuring the router so that some of them have static addresses while other computers have dynamic address(different address each time it requests for one). I am pretty sure you are asking yourself, so what is static ip?

Static ip means that a particular computer will always get the same ip address. In the case of static ip, whenever you turn on the computer, the computer will inform the router what its address is.

So how would you go about achieving it?

For my explanation, i will be using the Linksys BEFW11S4 router. Most other routers should work in a similar manner. But the important thing is the idea behind it.

• First, you must login to your router(for mine i enter 192.168.1.1 in my webbrowser address bar) and then a dialog box should pop up asking for your password.
• 
• After this is done, you will see a window similar to this.
• 
• Then click on the DHCP tab, which would bring up a screen that looks something like this.
• 
• The addresses handed out by the linksys router usually starts at 192.168.1.100. But if you want to manually set the addresses for some of the computers, you will want to change the starting ip address in order to avoid any conflicts. If we use the university analogy, once we name a building and that building name cannot be changed(static ip), that name should be off limits to others. In order to do that, we need to set the "Starting IP Address" so that the router does not hand out those addresses that have already been taken. Depending on how many static ip u have setup, the "Starting IP Address" should be set accordingly. So if u have 3 computers and 2 of them have static ip, you can put in 192.168.1.102 under the "Starting Ip Address" field(or higher if you want but i am assuming you have as static ip 192.168.1.100 and 192.168.1.101 for those 2 computers). So when the other computers dynamically asks for an ip from the router, it will only hand out ip address that is 192.168.1.102 or higher. It should look something like this.
  
• 

In general, if u have setup X static ip then the "Starting IP Address" should be 192.168.1.(100+X).

This achieves our goal of having both static and dynamic ip addresses.

More Resources:

Difference between Static and Dynamic IP.
If you wanna know how to setup static ip, microsoft has an article on it.