Free network & DNS tools for sysadmins and engineers
A small, focused set of IT operations utilities that run in your browser — no accounts, no installs, and nothing you type is stored.
Use the CIDR subnet calculator to plan IPv4 address space, work out host counts and subnet masks, split a block into VLANs, or summarise routes. Look up who owns an IP and pull every DNS record for a domain with the reverse DNS & PTR lookup tool. And when you change a record, confirm it has rolled out worldwide with the global DNS propagation checker. Tighten email deliverability and stop spoofing with the SPF, DKIM & DMARC checker, which validates your records and generates correct ones. And when you're standing up a new network, the DNS & DHCP planner turns a subnet into a full scope plan — gateway, static block, DHCP pool, exclusions and reservations — then exports matching A/PTR records and ready-to-paste ISC dhcpd and Windows DHCP config. Each tool is free, works on IPv4 and IPv6 where relevant, and is built for day-to-day network and systems administration.
Also see: Security Operations · GRC Tools · OSINT Tools · theadminstack.com