Click the DNS Settings button on the page to add DNS server(s) ORF will use for lookups, set the timeout, configure DNS caching and other lookup parameters.
Select the DNS resolver here. For more information on resolvers and their use cases, consult the DNS topic.
Using built-in resolver is advised in practically all cases.
The external resolver relies on external DNS servers for DNS access. Configure DNS servers here.
Click the New button and enter the name or the IP address to the dialog input. Using IP addresses to define a server is recommended. To resolve the name you entered into an IP address, click the Resolve to IP button.
Make sure to add only such DNS servers which meet the requirements described in the DNS topic.
You can modify the settings of an existing DNS server or remove it from the list by selecting it and clicking the Modify or the Delete buttons.
On startup, ORF picks the first DNS server in the list and performs all required lookups using this server. If any DNS error occurs – including network errors and timeouts – and you have additional DNS servers configured, ORF switches to the next DNS server from the list and tries the failed lookup again using the new server. If no DNS error occurs, subsequent lookups will be performed using this server, otherwise ORF continues the search for a working DNS server. If none of the DNS server found to be working, ORF gives up the DNS lookup, logs an error and proceeds with the rest of the tests.
Click the Check Health button to perform a test of the resolver you configured in ORF to see whether it works properly.
For more information, see the DNS Health Test section.
When using the external resolver, the caching feature of ORF can hold DNS lookup results in an internal cache for a user-specified time. This helps speeding up filtering on systems with very high load and reduces the bandwidth and DNS load on the DNS servers.
For more information, see the DNS Cache Settings section.
This feature is not available with the built-in resolver, which has its own efficient caching mechanism.
By clicking the Advanced button, you can configure additional parameters like DNS timeouts.
For more information, see the Advanced DNS Settings section.