Overview

Periodically, users connected to Kerio Control may lose Internet connectivity. Kerio Control is generating such entry in Error logs:

DNS response timeout, Kerio Control Web Filter categorization disabled. Serial number: ko-197974

After Kerio Control is restarted, the Internet access is restored.

Diagnosis

Kerio Control sends automatic DNS check queries to reach Kerio update servers. If the response is not being received for 10 times in a row within 1 minute, Kerio Control generates the above log. As a result, the Web Filter is considered as not reliable and it's showing as not activated or disabled in Kerio Control Webadmin. This might indicate issues with ISP, DNS configuration, or slow Internet link speed. After 1 hour, Web Filter functionality should be reverted to normal operation. If no, please refer to the solution below.

Solution

1. Login to Kerio Control console via SSH.
2. Execute the following commands to disable Reliability detection and to reset timers if Web Filter is already disabled:
   1. cd /opt/kerio/winroute
   2. ./tinydbclient "update SiteFilter set DetectReliability=0"
   3. /etc/boxinit.d/60winroute restart

Note: the last command will restart Kerio Control, so make sure to execute it outside of business hours.

Testing

The Error log entry is no longer generated and the Reliability configuration was changed successfully.