DNSFilter Knowledge Base

Changes that you make to your policy in the dashboard are reflected across our server fleet instantaneously. There are no delays for DNSFilter enforcing your changes.

However, DNS record information is usually cached (stored on your local browser, computer or network forwarder) for a specific amount of time; anywhere from 5 minutes to 8 hours is normal.

Policy Changes

Whitelisting Domains

When adding domains to a policy's whitelist, or deselecting categories from being blocked, you can expect to see the changes reflected in your network/computers within 30 seconds. DNSFilter block pages have a 30-second cache time (TTL), so there should normally be no need to clear the cache on your computer or browser. This is not gauranteed, as Chrome and some networking devices force a minimum cache time (TTL) of 60 seconds or more.

Blacklisting Domains and Changing Policies

When adding domains to a policy's blacklist, selecting additional categories to be blocked, or assigning a different policy to a network, domains may have been visited recently on computers in your network, and therefor the cache time (TTL) as set by the domain's DNS administrators, could take minutes or hours to expire.

Filtering Schedule TTL

If you have a filtering schedule applied, DNSFilter will prefetch and reduce the TTL values of domains on your policy so that domains are allowed/blocked at the precise times you've set on your filtering schedule.

Clearing your Cache

If you are encountering issues with content filtering, such as blocking not working according to your policy, we ask that you first clear both your system cache and browser cache. Instructions to do this are below:

Browser Cache

Google Chrome (Windows and Mac):

  1. In a new tab, type the following into the address bar and hit enter: chrome://net-internals/#dns
  2. Click the button labeled "clear host cache"

Firefox:

  1. Type about:config in Firefox’s address bar and acknowledge the warning that appears
  2. Find an entry called network.dnsCacheExpiration and set it’s value to 0 (If there’s no such entry, create a new integer item with the name above and a value of 0)
  3. Now go back and change the value to 3600

Safari (Windows and Mac):

Resetting the DNS Cache in Windows automatically flushes the DNS cache on Safari. Nothing to do here!

Operating System Cache

Windows 7

  1. Press ⊞ Win + X
  2. Right-click Command Prompt and select Run as Administrator.
  3. Run the following command and hit enter:
    ipconfig /flushdns

Mac OSX 10.9 and Later:

  1. Launch the Terminal application
  2. Run the following command and hit enter:
    sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder

Mac OSX 10.8 and Earlier:

  1. Launch Terminal (under Applications/Utilities)
  2. Run the following command and hit enter:
    sudo killall -HUP mDNSResponder

Linux (Ubuntu)

  1. Open a terminal window.
  2. Run the following command and hit enter:
    sudo service network-manager restart

What's Next

Policies