Had a strange problem recently whereby a Windows XP Pro machine didn’t seem to want to connect to the internet, or so it appeared. I tried accessing google.com and hotmail.com and both returned error pages as did MSN Live Messenger when trying to log in.
I checked the BT HomeHub and the broadband light and LAN lights were on but I rebooted the hub just for good measure.
I then connected my iPhone to the hub via wi-fi and it was instantly online so no problem with the broadband connection itself and access to google.com and hotmail.com was fine.
The ethernet cable from the router to the computer was seated correctly, the XP machine had picked up an IP properly from the router’s DHCP, it all seemed ok.
I tried accessing bbc.co.uk just in case it was a caching error and to my surprise it loaded the page without delay. After trying a few others, skynews.com, digg.com, etc I established it was just a handful of sites affected.
Rather than the usual, “just give it a reboot” I wanted to see if I could find a fix without restarting. Since almost all site except ones used regularly on that machine were working it had to be some sort of DNS or cacheing issue. I’d tried emptying internet explorer’s cache and relaunching IE7 which had not effect. I then found firefox hiding on the system and never used so I tried that and same problem, so it wasn’t a program specific cache it was a global cache somewhere on the machine and there appeared to be a very easy fix, just clearing the local DNS cache from the command prompt.
Simply open up a command prompt window (windows key+R, then type “cmd” and hit return). Once in command prompt just type:
This will clear any local DNS cache which Windows XP has created to speed up access to some sites you have recently visited. After flushing the DNS Internet Explorer opened google.com and MSN Live messenger signed in without a hitch and no need to restart either 🙂 You can edit your Windows registry and set the local DNS to never cache or have a much shorter cache refresh period but I didn’t bother in this case.
I know this is common knowledge to a lot of people but it should serve as warning when testing for an internet connection, don’t simply try to access google.com, or some other well known site that may be in a corrupt local dns cache. It’s the first time I’ve been caught out by it and it’ll certainly be my last.