dnsmasq

Dnsmasq provides network infrastructure for small networks in a single lightweight program, covering DNS, DHCP, router advertisement and network boot together.

Combining those is exactly right for its target. A home router, a firewall or a small office server needs all four services and has no capacity to run four separate daemons, and the pieces are naturally connected: machines configured by DHCP have their names automatically included in the DNS, which is the single most useful thing a small network wants and which separate tools make surprisingly awkward.

Its footprint explains where it ends up. Designed for resource constrained routers and firewalls, dnsmasq is also widely used for smartphone tethering and portable hotspots, and to support virtual networking inside virtualisation frameworks. Very few users know they are running it.

The DNS side forwards all query types upstream and caches A, AAAA, CNAME and PTR records, plus DNSKEY and DS when DNSSEC is enabled, with DNSSEC validation available against upstream replies to protect against spoofing and cache poisoning. Local names come from /etc/hosts, from DHCP, or from configuration. An authoritative mode exports local names to a global zone with zone transfer to secondaries. Specified subdomains can be directed to their own upstream servers, which makes VPN configuration straightforward. DHCP supports static and dynamic leases plus stateless DHCPv6, and the PXE server handles netboot menus, multiple architectures and proxy mode.