Windows XP and DNS

DNS or Directory Name Service is how your browser finds a website from a name.  For example when you type in csispecialist.com your browser looks it up on a DNS server and gets the correct address and then opens the page for you using that address.   It would be like asking where the local pub is and someone telling you it is on 712 Main Street so you can then can go to that specific address.

Most DNS servers today update their information every 2 hours and sometimes even less.  However when XP was around the servers only updated every 24 hours or more.  If you are still running XP you can change this value with a registry edit.  This edit works on newer systems as well but most current operating systems take the shorter time into account.

The registry edit is as follows:

Under:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\ Services\Dnscache\Parameters
Add the DWORD value: MaxCacheTtl

then set the value (in decimal) to:  7200

That sets it to expire entries that are 2 hours or older.


Another thing that DNS does is cache negative entries.  These are simply entries that did not resolve to a legitimate address.   If you use multiple DNS providers or are checking to see when a site comes up after setting it’s DNS this could also be useful.  To do this there is another registry setting you can put in.

 

The registry edit is as follows:

Under:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\ Services\Dnscache\Parameters
Add the DWORD value: MaxNegativeCacheTtl

then set the value (in decimal) to:  0

This will tell XP to stop caching stuff that’s not there.

After you have applied either or both of these registry settings you can reset the DNS cache on your computer by opening the command prompt and typing the following:

ipconfig /flushdns

Your computer should return:

“Windows IP Configuration

Successfully flushed the DNS Resolver Cache.”