If you are having trouble reaching specific websites, you may have a corrupted or out-of-date DNS cache. This cache can be cleared on your local Desktop or laptop computer and, if you have a DNS server installed on your internal network, on the server that runs that service.
Windows Desktop or Laptop
Rebooting the computer clears the DNS client resolver cache. However, you can also clear the cache without restarting by opening a command window (WIN+X) and entering the following at the prompt:
After hitting Enter key, the following message will appear: Successfully flushed the DNS Resolver Cache.
Mac OS X
Open a Terminal window and enter the following syntax:
sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder; say DNS cache flushed
You will prompted for your password. When you hear "DNS cache flushed" the command was successful.
Windows Server DNS Server
There are 2 ways to clear the DNS cache on a DNS Server in Windows. One way is to restart the DNS Server service. The other is to open a command prompt as administrator and enter the following:
dnscmd ServerName /clearcache
where ServerName is the NetBIOS name of the DNS server.
This could vary a little depending on distort. Here is an example of what you would enter in a Terminal window:
sudo /etc/init.d/dns-clean restart
For other dittos, contact support.