Network tools for quick diagnostics

Some network questions can be answered offline — subnet maths is pure arithmetic — while others, like 'what is my public IP?', can only be answered by asking a server on the internet. This page keeps both kinds together and labels them honestly.

The IP and DNS tools send your request directly from your browser to the named public service (ipapi.co and Google Public DNS). They do not pass through an ITInfoByte server, and nothing is logged by this site.

Lookups (use an external API)

These need a remote service to answer.

What Is My IP Address?Look up your public IP along with the city, region, and ISP it resolves to.Uses API DNS Record LookupQuery A, AAAA, MX, and TXT records for any domain through Google's public resolver.Uses API SPF, DKIM & DMARC CheckerGrade a domain's email authentication: SPF lookups and includes, DMARC policy, DKIM key size and fixes.Uses API

Address planning

Subnetting and CIDR maths — nothing leaves your device.

IP Subnet CalculatorNetwork, broadcast, mask, wildcard, host range and usable hosts from any IP and CIDR prefix.Local IPv6 Subnet CalculatorNetwork, range, exact address count, type and ip6.arpa zone for any IPv6 prefix, plus splitting into smaller subnets.Local VLSM CalculatorDivide an IPv4 network into subnets sized by host count, with masks, usable ranges, broadcasts and the leftover free blocks.Local IP Range to CIDR ConverterRange to minimal CIDR blocks, CIDR to first and last address, and merge IP lists into the fewest blocks. IPv4 and IPv6.Local

References and estimates

Offline lookups and quick sums.

Port Number LookupSearch well-known TCP/UDP ports by number, range or service, with IANA vs de facto use and security notes.Local HTTP Status Code LookupSearch every HTTP status code by number, class or keyword, with causes, fixes, RFC, caching and retry advice.Local Download Time CalculatorHow long a file takes at your connection speed — and why Mbps isn't MB/s.Local URL Encoder / DecoderPercent-encode text for query strings, or decode an encoded URL back to readable form.Local

Good to know

Why does DNS lookup use Google?

Browsers cannot send raw DNS queries, so the tool uses Google Public DNS's DNS-over-HTTPS JSON API. Only the domain name and record type you enter are sent.

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