The next option, enabled by default, is Enable DNSSEC Support. DNSSEC is a means of protecting DNS data from attacks which use forged or manipulated DNS data, such as DNS cache poisoning. If you enable it and the upstream DNS server to which you will be forwarding DNS requests does not support DNSSEC, however, DNS resolution may not work.

The Enable Forwarding Mode checkbox allows you to control whether Unbound will query root servers directly (if this option is unchecked) or if queries will be forwarded to the upstream DNS servers. You should only enable this option if  the upstream DNS servers are trusted. If you have enabled DNSSEC support, and you consider this to be important, you should also make sure the upstream DNS servers provide DNSSEC support. Forwarding mode is necessary if you are using a multi-WAN configuration which does not have default gateway switching.

The Register DHCP leases in the DNS Resolver option allows you to register DHCP static mappings. This in turn enables the resolving of hostnames that have been assigned IP addresses by the DHCP server. The Register DHCP static mappings in the DNS Resolver  option is similar to the Register DHCP leases in the DNS Resolver option, except the former allows you to register DHCP static mappings instead of DHCP leases. The Display Custom Options button reveals a textbox when you click on it. You can enter any additional parameters here.