DNS Cache-Poisoning

Sometimes (especially in China) it might happen that you connect through a VPN but still cannot access certain sites, like YouTube or Facebook. The reason for this is most likely DNS Cache-Poisoning.

As you might know every Hostname (e.g. youtube.com) leads to a specific IP address. When you want to visit Internet sites your computer asks a Nameserver which IP it to connect to. An often used analogy to explain the Domain Name System is that it serves as the "phone book" for the Internet by translating human-friendly computer hostnames into IP addresses.

DNS Cache-Poisoning means the DNS-System purposely leads your computer in the wrong direction in order to hinder your access to certain resources. This practice is very prevalent in certain countries. By using YouPrivateVPN this can't happen, as all requests are answered by our own, uncensored, Nameservers. Unfortunately, there are sometimes remnants of these "poisoned" (misdirected) DNS entries on your computer. These entries result in your computer connecting to incorrect IP's, even when you are connected via YourPrivateVPN. So, if you notice that you are being redirected to the wrong sites, you will need to get rid of these "scraps".

 

Microsoft Windows (all versions)

The Windows DNS-Cache can be deleted by entering the following command into the Windows commandline:

ipconfig /flushdns

 

Mac OS 10.5 (and up)

You can delete the DNS-Cache on a Mac by entering the following command into the Mac OS terminal:

dscacheutil -flushcache

 If that doesn't work, try:

sudo dscacheutil -flushcache

 

Firefox Browser (all versions and all os)

Start Firefox, enter “about:config” in the address bar and press enter. If you are using Firefox 3+ then you will see a warning page, just click the “I’ll be careful, I promise” button.
When you enter the "about:config" interface, you'll see many rows of preference data. Simply right click anywhere in a blank area in those rows of data and select “New” -> “Integer”, Then type (or paste):

network.dnsCacheExpiration

which becomes the preference name, hit enter, and type “0″ as the integer value, hit enter. Right click again and select “New” -> “Integer”, again. This time type (or paste):

network.dnsCacheEntries  

as the preference name, hit enter and, again, use “0″ as the integer value, hit enter. Done.

 

General

You will also want to clear the cache in your browser. If you are still unable to connect or can't get the commands to work for you, reboot your machine then connect immediately via the VPN, before opening your browser.