Sunday, January 25, 2009

Network troubleshooting | DNS Problem | My IP Address Guide

Here is a quick guide to basic network troubleshooting, how to identify DNS problem and how to check your own IP address on desktop computers on Windows and some Linux, a lot of this guide will cover wireless since most of the desktop and laptop users this today uses wireless connection to connect to their network or their internet, still a lot of this will also work on wired network.

Now let begin -

Problem 1 - I can connect to my wireless network, can't surf the net and windows say Limited connectivity or Local connection only, what am I gonna do?

Ans. this problem could be cause by lack of DNS entry on your router or DNS entry on your computer.

to check on Windows if you have a DNS entry type

On Windows
ipconfig /all <- usually this would show all the details of your card, you should be able to see if there is a DNS entry assigned to it, there is a class c IP address assigned to you usually start with 192.168.*.* , and also check if there is a gateway which should be your routers IP address, if one of these is missing then you have to correct it.

To renew your IP Adress on Windows use the command

ipconfig /release
ipconfig /renew

On Linux
ifconfig -a <- should show you the IP address and your interface details, such as IP, MAC address.

to check for gateway on Linux you need to issue the command
route <- you will be presented with a routing table, default Gateway should be defined to check if you have a DNS entry on Linux issue the command cat /etc/resolv.conf <- it should return something like "nameserver IP ADDRESS HERE" another way of identifying DNS problem is by issuing the following command Linux and Windows nslookup 72.14.207.99 <- if you receive a reply like the one below then its not a DNS problem

Name: eh-in-f99.google.com
Address: 72.14.207.99

Now that we have eliminated DNS problem

You have to check your routers configuration and make sure it not your internet provider that having connection issue.

use the ping command
ping yourgatewayiphere <- you should get a reply something like the one below Pinging 72.14.207.99 with 32 bytes of data:
Reply from 72.14.207.99: bytes=32 time=693ms TTL=238


Problem 2 - Cannot connect to the network at all

Make sure that wireless is turned on, and that your router is broadcasting SSID and has DHCP on, also make sure that the router is turned on, otherwise you will need to connect using a cable and see if you can connect.

NOTE: if all else fails try restarting(turn on/off) your router, most of the time this fixes it.


Thats it for now.

4 comments:

John said...

Very good troubleshooting steps from one computer geek to another. DNS can be a real pain to troubleshoot.

lara tomb said...

Good post...I was able to renew my IP using your tips and even confirmed the change in IP through Ip-details.com

Melissa Lee said...

I tried all of these, it says cannot be found when I enter ping yourgatewayiphere
I just want my laptop to connect without having to be pluged in with the eathernet cable.

Jonathan Ty said...

You need to get your gateway Ip using this command

ipconfig /all

Before doing the above command make sure you are connected to your router wired or wireless.

If your unable to connect wireless t your router on your laptop make sure wifi is not disabled on you laptop, using the button on your laptop which you might have accidentally disabled.

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