Subnets, DNS and port checks, without the guesswork.
Free tools network engineers use daily: work out a subnet plan, look up DNS and mail records, test whether a port is reachable, and draw the network diagram. No sign-up needed.
Most used tools
Subnet Calculator
IP & MaskIPv4/IPv6 CIDR math, broadcast, wildcard & 32-bit allocation bitmap.
DNS Lookup
ResolutionQuery A, AAAA, MX, TXT, NS, and CNAME records with TTLs and zone export.
Ping & Latency
DiagnosticsMeasure round-trip time, min/avg/max, jitter, and packet loss via TCP handshake.
Traceroute
RoutingMap router hops and isolate network latency spikes across public paths.
Port Checker
ConnectivityTest if public TCP ports (22, 80, 443, 3306) are open, filtered, or closed.
Topology Studio
DesignDesign topologies with 35+ vendor models, auto-layout & SVG/PNG export.
All Tools Directory
23 tools available
ASN and IP Prefix Lookup
Find the owner of an IP address or AS number and every prefix an AS announces, from live BGP data.
Bandwidth and Transfer Time Calculator
How long will a transfer take, or how fast a link do you need? With real-world efficiency and TCP window limits.
Blacklist Check
Check if an IP or domain is listed on major spam and malware DNSBLs.
DKIM Checker
Validate a domain's DKIM record: key size, flags and problems. Finds the selector automatically.
DMARC Lookup
Check a domain's DMARC policy to ensure proper email authentication.
DNS Lookup
Query A, AAAA, MX, TXT, and NS records for any domain in one lookup.
Email Health
Comprehensive diagnostic of your SPF, DKIM, and DMARC configurations.
HTTP Header Checker
View every HTTP response header of a website and get a graded security review (HSTS, CSP, clickjacking, cookies).
IP Address Converter
Convert IP addresses between dotted, decimal, hex, binary and octal; expand and compress IPv6; see the address type.
IP in Range Checker
Check which IP addresses fall inside which CIDR blocks or ranges, IPv4 and IPv6, in bulk.
MAC Vendor Lookup
Identify the hardware manufacturer (OUI) of any MAC address.
MTA-STS, TLS-RPT and BIMI Checker
Check a domain's MTA-STS policy, TLS-RPT reporting and BIMI logo, graded with fixes.
MX Lookup
Check a domain's Mail Exchange records to troubleshoot email routing.
Network Diagram Maker
Drag-and-drop network diagrams with FortiGate, Cisco, Meraki & Palo Alto icons — export as PNG or SVG.
Ping Test
Measure round-trip latency and packet loss to any host from our server.
Port Checker
Verify if a TCP port is open and accepting connections on a remote server.
Redirect Checker
Trace a URL through every redirect with the status code of each hop and find loops, long chains and downgrades.
SSL Certificate Checker
Check any site's SSL/TLS certificate: expiry, issuer, chain, TLS version and host-name match, graded A to F.
Subnet Calculator
Calculate subnets, broadcast addresses, wildcard masks, and host ranges.
Traceroute
Map the exact path and router hops packets take across the internet.
Website Down Checker
Is it down for everyone or just you? Request a site from several countries and compare status and timing.
What is my IP?
Instantly discover your public IPv4 address, ISP, and approximate location.
WHOIS Lookup
Query RDAP/WHOIS databases to find domain registration and ownership info.
Engineering reference & cheat sheets
Standardized technical parameters, port assignments, and CLI commands for daily operations.
| Port | Protocol | Service | Description | Action |
|---|---|---|---|---|
| 22 | TCP | SSH | Secure Shell remote terminal access | |
| 53 | UDP/TCP | DNS | Domain Name System resolution | |
| 80 | TCP | HTTP | Hypertext Transfer Protocol | |
| 443 | TCP | HTTPS | HTTP over TLS/SSL encryption | |
| 3389 | TCP/UDP | RDP | Microsoft Remote Desktop Protocol | |
| 8080 | TCP | HTTP-ALT | Alternative web proxy & development servers | |
| 123 | UDP | NTP | Network Time Protocol clock synchronization | |
| 161 | UDP | SNMP | Simple Network Management Protocol |