Network Tools
Most network problems start with two questions: what does DNS really return for this name, and which addresses belong to which network? Guessing at either wastes hours.
2 free tools
Network Tools
About these network tools
The network tools answer both. Look up DNS records and watch a change spread across probes in different countries, or work out network and broadcast addresses, split a block into subnets and plan variable-length subnets for a new site — with exact IPv4 and IPv6 arithmetic.
Why use them
Real DNS answers
The DNS Checker queries public resolvers and real probes in 14 countries — nothing is simulated or cached for long.
Exact subnet maths
Subnet calculations use 128-bit integer arithmetic, so even the largest IPv6 prefixes are counted exactly, and they run entirely in your browser.
Plans you can export
Copy any result, or export subnet lists and VLSM plans as CSV or JSON for your documentation or IPAM.
Frequently asked questions
Do these tools send my IP addresses anywhere?
The IP Subnet Calculator runs entirely in your browser; addresses never leave your device. The DNS Checker has to query DNS from a server, so the domain you check is sent to our server and to the public resolvers and probes when you press Search — it is not stored or logged.
What is CIDR notation?
CIDR writes a network as an address plus a prefix length, like 192.168.1.0/24: the first 24 bits identify the network and the remaining 8 bits number the hosts. It replaced the old class A/B/C system in 1993 and is used for both IPv4 and IPv6.