If your Internet is down, you probably can’t read this! It would be better if you save this page locally for a rainy day! This page will also give you a better understanding of what goes behind the scenes that makes your net… work…!
At first you need a brief introduction of how your Internet works. You, as the user, are given a cable modem or DSL Modem from your service provider (ISP) that connects to the network either via coax (thick cable) or your phone line. The modem, in turn, establishes a connection with the ISP’s network. The network has a DHCP server that gives the modem an IP address. That address is accessible from the Internet (Public IP). If you have no clue what I am talking about, then please read the article that addresses IP found here.
Now, either you connect your computer, wired or wireless, to that modem or connect a wired or wireless router so you can share your connection to multiple machines/devices.
Are you still with us?
If you are plugged directly into the modem, it will give you a private IP address that is NATed out to the public IP.
If your setup is such, then it will be easy unless you are going to switch computers. Due to security restrictions, you will need to restart the modem to give the machine an IP address. We recommend you get a router, which will allow you to swap machines and share the net with multiple machines.
Now lets move on to how to troubleshoot. Take a deep breath! Now let us take the plunge…
What do you mean by ‘the Internet’s down’?
After you go through the normal steps of denial, rebooting, blaming your ISP, rebooting, cursing…. Check out these steps:
1. Before you do anything else, first restart your modem and then wait for it to come back online. Once that is done, restart your router.
2. If you don’t have a router, reboot your computer and then the cable modem.
3. Once all the modems lights are lit and the activity lights are blinking, the net should be back up. If all the lights do not come on, check that all your cables are secure and then call your ISP.
4. Open a new browser window and try to get the site: http://www.worldstart.com. If the site comes up, it is good. If not, continue reading.
5. Go to Start>Run and type in CMD
6. Type Ipconfig /all
7. Make note of your default gateway and DNS servers.
8. Ping your default gateway. Do you get a response?
9. Ping one of the DNS servers. Do you get a response?
10. Type ping www.worldstart.com. Do you get a response?
If all else fails, you could use traceroute to find out where you are getting stuck. Traceroute is a command which can show you the path a packet of information takes from your computer to one you specify. It will list all the routers it passes through until it reaches its destination, or fails to and is discarded. In addition to this, it will tell you how long each ‘hop’ from router to router takes. To do this, just go to Windows, select Start > Programs > Accessories > Command Prompt. When a window pops up, enter the word ‘tracert’, followed by a space, then the domain name. If it timed out after line 1, you would know there was a problem connecting to your ISP in which case you will not be able to access anything on the Internet. It is generally recommended that if you have a website that is unreachable, you should use both the traceroute and ping commands before you contact your ISP to complain. More often that not, there will be nothing your ISP or hosting company can do about it.
Similarly, there are a number of network issues where there are two DHCP servers giving out IP addresses. If you have a router, you need to make sure it is in the same internal range as the cable modem. If your ISP router is 192.168.1.1, make your router .2. And if possible, disable the DHCP on the original. That should do the trick most of the time.
Best of luck!
~Zahid H Javali