DNS Cache Problems?

Question

I am not a extremely computer smart guy, but it has come to my attention that the DNS cache might be the cause of my internets recent slowed activity.

I have found through research that I have to flush or clear the DNS cache, but have no idea how.

Could somone explain exactly what is wrong with my computers internet, and how it got that way. Can you get this DNS cache problem from a wireless outlet, like a laptop, or even something like a wii or PSP?

Answer 1

The DNS cache is the way that your computer finds websites on the internet.

Each computer has a unique number assigned to it, however because it is so hard to remember numbers DNS turns them into names like greatbritishdebate.info

Anyway, its this list of numbers next to the names they belong to.

I doubt this is the cause though, if you are using internet explorer, Goto Tools->Delete  Browsing History or Tools->Internet Options->Temporary Internet Files->Delete

this may help as your computer keeps a copy of all websites on your computer, and checks to see if the copy it has is out of date before loading a fresh one, and this will remove the old files

To clear the DNS Cache, goto Start menu->Run->type in "cmd" without quotes->click ok

A black box should come up, type (without quotes)

"ipconfig /flushdns"

and press enter and it will clear the dns cache.

Hope This helps

Answer 2

I am not sure about PSP or Wii but you can most definitely have problems with the DNS cache on a laptop, or any other computer that caches DNS results.

Flushing the DNS cache (keep in mind I use Linux and Windows, the Mac instructions are as best as I can do):

1) Open a command prompt / shell / terminal:

Windows: Click Start -> Click Run -> Type "cmd" without the quotes -> Click OK

Mac OSX: Terminal is located in the Utilities folder (?)

Linux: Depends on current Window Manager and setup, look for Terminal in the application menu.

2) Type the following command, without the quotes or OS name, and press enter:

Windows: "ipconfig /flushdns"

Mac OSX 10.5.1 or older: "lookupd -flushcache"

Mac OSX Alternate: "dnscacheutil -flushcache"

Linux: "/etc/init.d/nscd restart"

3) The DNS cache will now be cleared, if you continue to have problems then either

A) The problem is something wrong with your internet provider's DNS servers, call their customer support

B) The problem isn't related to DNS at all and you need to explore other possibilities.

What DNS caching is:

Here's what happens, when you type a web address into your browser (eg. www.yahoo.com) your computer asks your internet provider's computer (the DNS server) for the IP address associated with that web address.  It's similar to looking up a phone number, you know someone's name so you look up their name in a phone book to get the phone number.  In this case Yahoo's IP address (phone number) is 69.147.76.15

Now, when your internet provider's DNS server tells your computer the IP address your computer remembers that IP address for a while so that if you return to the same web site it doesn't need to look it up again.  This is the DNS cache.  If your internet provider's DNS server is having problems it could send you the wrong IP address which your computer will then remember.  This is when you need to flush the cache.