====== PFSense - DNS - DNS Resolver - Prefetch Support ======

Prefetch keeps popular items in the cache from expiring.

Navigate to **Services -> DNS Resolver -> Advanced Settings**.

In **Advanced Resolver Options**:

  * Prefetch Support:  **Checked**.

<WRAP info>
**NOTE:**  It will only look up or prefetch a record if a client requests that record and the ttl is within 10% of expiration.

  * Lets say www.domain.com had a ttl of 600 seconds.
  * Client asks for www.domain.com while the ttl is at 300 seconds.
  * The record is returned to the client.  No prefetch done as the ttl is only at 50%.

  * Now another client asks for www.domain.com while there is say 59 seconds left on the ttl.
  * Client will get their answer, and then unbound will go resolve www.domain.com again to refresh the cache.

</WRAP>