Networking and sysadmin tools on it.you are built for the daily diagnostic and configuration work that network engineers, sysadmins, and DevOps professionals deal with: looking up DNS records to diagnose propagation delays, checking what IP address a domain resolves to, calculating subnets for a new VLAN, identifying which service owns a well-known port, or building a cron expression for a scheduled backup job.

The DNS, IP, and WHOIS lookup tools make server-side queries to external data sources — the input (a domain or IP address) is sent to the server to perform the lookup, but it is never stored. All other tools (subnet calculator, port reference, cron builder) run entirely in your browser with zero data transmission.

Who uses these tools?

Network engineers

Calculate subnets, verify CIDR ranges, look up BGP routes, and diagnose DNS propagation issues.

Sysadmins

Identify open ports, check WHOIS ownership, run DNS queries across record types, and build cron job schedules.

DevOps & SREs

Quickly check DNS TTLs during deployments, verify IP geolocation, and reference port numbers for firewall rules.

IT support teams

Look up a customer's IP address, check domain registration details, and reference HTTP status codes during incident response.

What's in this category?

IP Address Lookup

Look up geolocation, ISP, and network info for any IP a

DNS Lookup

Query DNS records for any domain: A, AAAA, MX, TXT, CNA

WHOIS Lookup

Check domain registration info and ownership details.

Common Ports Reference

Searchable list of all well-known and common network po

HTTP Status Code Reference

Complete reference for all HTTP status codes with expla

Subnet Calculator

Calculate subnet masks, network ranges, and host counts

Tool types in this category

Type	Count	How it works	Privacy
Browser-only	4	Runs entirely in your browser — no server requests	No data leaves your device
Server-assisted	3	Requires a server query (DNS, WHOIS, IP lookup)	Input sent to our server — not stored

Key concepts

DNS (Domain Name System) — The internet's distributed directory — translates human-readable domain names (example.com) into machine-readable IP addresses. Record types: A, AAAA, MX, TXT, CNAME, NS, SOA.

CIDR notation — Classless Inter-Domain Routing — a compact way to express IP address ranges. /24 = 256 addresses (254 usable hosts), /16 = 65,536 addresses. Used in firewall rules, routing tables, and VPC configs.

WHOIS — A query-response protocol for looking up registration data for domain names and IP addresses — registrar, owner, registration/expiry dates, and nameservers.

BGP (Border Gateway Protocol) — The routing protocol that governs how packets are routed across the internet between autonomous systems. ISPs and large enterprises run BGP.

TTL (Time to Live) — In DNS, TTL is how long resolvers cache a record before re-querying. Low TTL = faster propagation during changes; high TTL = less DNS traffic but slower updates.

Cron expressions — A 5-field time specification used by Unix cron and tools like Kubernetes CronJobs. Fields: minute hour day-of-month month day-of-week. Example: 0 2 * * 1 = 2 AM every Monday.

Frequently asked questions

What is DNS propagation and why does it take time?

When you change a DNS record, the old record is cached by resolvers worldwide for its TTL duration. Until each resolver's cache expires, some users will still see the old record. Propagation typically takes minutes to 48 hours depending on the TTL.

What is the difference between a /24 and a /16 subnet?

A /24 subnet has 256 addresses (254 usable hosts) and a mask of 255.255.255.0. A /16 has 65,536 addresses (65,534 usable) and a mask of 255.255.0.0. Smaller numbers = larger subnets.

What is the difference between TCP and UDP?

TCP (Transmission Control Protocol) is connection-oriented and guarantees ordered, reliable delivery via acknowledgements. UDP (User Datagram Protocol) is connectionless and faster but has no delivery guarantee. Use TCP for HTTP/HTTPS, SSH, FTP. Use UDP for DNS, VoIP, video streaming.

What well-known ports should I know?

Key ports: 22 (SSH), 25/587 (SMTP), 53 (DNS), 80 (HTTP), 443 (HTTPS), 143/993 (IMAP), 110/995 (POP3), 3306 (MySQL), 5432 (PostgreSQL), 6379 (Redis), 27017 (MongoDB), 3389 (RDP).

What does WHOIS reveal about a domain?

WHOIS shows the registrar, registration and expiry dates, nameservers, and sometimes registrant contact details (though privacy protection services now hide most personal data by default).

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