Windows 7 and DNS Server woes

Problem !

When I moved into my apartment this weekend I was unable to connect to the internet which lead to emotions of utter disbelief followed by despair and finally by obsessive compulsion and irritability until fixed. Despite the best intentions of my operating system to automatically diagnose and correct the problem it couldn’t. Not holding any grudges, we all have our limitations. I was stuck with –

Windows can’t communicate with the device or resource (Primary DNS Server).

Solution !

I knew something was wrong with MY machine because by husband’s Macbook-Pro worked just fine. Damn. So here’s the deal, Windows 7 on Sony VAIO had set my DNS server to a static value. To make things work, I simply had to ask windows to obtain DNS server address automatically. Easy-peasy.

1. Select Start
2. Select Control Panel
3. Select Network and Internet
4. Select Network and Sharing Center
5. Select Change adapter settings (in the left corner)
6. Right-Click Local Area Connection and select Properties
7. Select Internet Protocol Version 4 (TCP/IPv4) and click Properties
8. Under General select Obtain DNS server address automatically and click OK

When and why does this problem occur?

Technically I don’t know (Now I do, see update below!). But generally, the problem seems common on a Sony VAIO running Windows 7, especially if you switch between networks.

Is this solution permanent?

Apparently not! The behavior seems a bit erratic with the DNS server being reset to its static value randomly between standbys and resets. If that happens you can repeat the steps above or even try resetting the TCP/IP stack. With Windows, you never quite know the mood its in ;-)

[Update – an hour later] Understanding why this happens (technically) ! See below an as-is explanation by my friend Amit.

Step 0: The n/w is down
Step 1: You see some wlans
Step 2: You select one
Step 3: Your NIC ( n/w interface card) and the router get familiar, they authenticate
Step 4: Now the connection is established @ the “PHYSICAL LAYER”
Step 5: You now need IP to talk TCP & UDP, so send DHCP request
Step 6: Get response back from the router. It should contain among other things your MAC ( for verification), your new IP, your gateway address ( same as the router’s IP ) and DNS settings ( DNS server IP, search strings etc)

Thats it … your n/w should now be up. In your case, if the setting is disabled (Obtain DNS through DHCP) your machine will continue to use the static DNS that you have set and ignore the one given by your router.

Thanks Amit :) Life makes sense again!

Conclusion:If you want to enable DHCP on a Windows 7 machine, simply select “Obtain DNS server address automatically” in the TCP/IP settings as show above. Happy surfing!