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.
Frequently asked questions
Are these IT Ops tools free?
Yes. Every tool under theadminstack.com/itops is free to use with no account, no sign-up and no API key. They are built for systems administrators and network engineers doing day-to-day work.
Is my data sent to a server?
It depends on the tool, and each one says so on its own page. The CIDR subnet calculator and the DNS & DHCP planner run entirely in your browser — nothing you type leaves your device. The reverse DNS lookup, DNS propagation checker and SPF/DKIM/DMARC checker have to query public DNS resolvers to answer at all, so the domain or IP you enter is sent to those resolvers. Nothing is stored or logged by TheAdminStack.
What tools are available?
Five: a CIDR subnet calculator for planning IPv4 address space, a reverse DNS and PTR lookup, a global DNS propagation checker, an SPF, DKIM and DMARC checker, and a DNS & DHCP scope planner.
How do I check whether a DNS change has propagated?
Use the DNS propagation checker. It queries public resolvers around the world at once and shows which have picked up the new record and which are still serving the cached one, so you can tell the difference between a change that has not rolled out yet and a change that was never made correctly.
Why is my email going to spam?
Usually because SPF, DKIM or DMARC is missing, misaligned or failing. The SPF, DKIM & DMARC checker validates the records you have and generates correct ones. There is also a longer walkthrough in Why your emails go to spam.
Who builds these tools?
They are built by TheAdminStack, alongside companion SecOps, GRC and OSINT tool suites.
Also see: Security Operations · GRC Tools · OSINT Tools · theadminstack.com