A forwarder is used with DNS server when it receives DNS queries that cannot be resolved quickly. So it forwards those requests to external DNS servers for resolution.
A DNS server which is configured as a forwarder will behave differently than the DNS server which is not configured as a forwarder.
Following are the ways that the DNS server behaves when it is configured as a forwarder:
* When the DNS server receives the query, then it resolves the query by using a cache.
* If the DNS server is not able to resolve the query, then it forwards the query to another DNS server.
* If the forwarder is not available, then it will try to resolve the query by using root hint.
