The first tab is labeled General Settings, and the first section on the page is General DNS Resolver Options. The first option is Enable, which enables Unbound, and is checked by default. The next option is Listen Port, which allows you to set the port used for responding to DNS queries. The default port is port 53 (DNS traditionally uses port 53 and the UDP, although DNS also uses TCP for responses larger than a datagram, including DNSSEC and some IPv6 lookups, so take this into account when creating firewall rules for DNS).
The Network Interfaces list box allows you to select which interface IPs are used by Unbound to respond to queries from clients. Queries to interfaces not selected are discarded. If Unbound is enabled, ...
