The DNS forwarder (Services > DNS Forwarder) is a powerful tool that allows fine-grained control over the DNS service provided to clients on a network. The DNS Forwarder refers to the dnsmasq daemon. For Unbound, see Unbound DNS Resolver.
The DNS forwarder will answer DNS requests from clients, and in turn attempt to resolve queries using all currently available configured DNS servers. This way, it is not necessary to configure public DNS servers directly on client systems.
If the DNS forwarder is enabled, the internal interface IP for pfSense will be handed out to DHCP clients as a DNS server. If the DNS forwarder is disabled, the DNS servers configured on pfSense will be handed out instead.
Optionally, the DNS forwarder can register hostnames from DHCP leases so that local hostnames can be resolved via DNS. The same can be done with static DHCP mappings. This should only be enabled on networks where the client hostnames can be trusted or controlled.
Host and domain overrides may also be entered which will be used in place of the responses that would have otherwise come from the upstream DNS servers. This can be used for Split DNS, or making undesirable domains (e.g. myspace.com) resolve to a non-existent IP address.
On pfSense 2.1 and later, Host Overrides work for both IPv4 and IPv6 addresses.
On pfSense 2.2, The DNS Forwarder is not active by default. It has been replaced by Unbound as a DNS Resolver. It may still be used, and is still active on upgraded configurations. To use the DNS Forwarder (dnsmasq) on 2.2, first disable Unbound and then enable the DNS Forwarder.
Important Note: This service should not be exposed publicly. Ensure inbound rules on WANs do not allow connections from the Internet to reach the DNS Forwarder service on the firewall.