Network Tools

ArrayKit's network tools cover the address math, DNS records and quick checks that sysadmins, network engineers, mail admins and students reach for. For IP planning, the CIDR / Subnet Calculator shows a block's network and broadcast addresses, mask and usable hosts, the Subnet Splitter divides it into equal subnets or sizes them by host count, and IP Range to CIDR turns a range into the fewest CIDR blocks. For DNS and email, the SPF Record Generator and DMARC Record Generator build and check the records that stop others sending mail as your domain, alongside DKIM, CAA, SRV and reverse DNS generators. To share, the WiFi QR Code Generator makes a code guests scan to join your network, and P2P File Transfer sends files between two browsers. The Download Time Calculator and Data Usage Calculator turn speeds and habits into transfer times and monthly gigabytes, and Port Number Lookup says what runs on a port. For debugging, the HAR File Viewer lays out a capture's requests and timings, the User Agent Parser and Set-Cookie Parser decode individual headers, and the MTU & MSS Calculator works out MSS for links and tunnels. Every tool except P2P File Transfer keeps your input on your device; that one sends files straight to the other browser, never to ArrayKit, and contacts a public STUN server only so the devices can find each other.

  • CIDR / Subnet Calculator — Calculate network, broadcast, host range and mask from a CIDR block.
  • IPv6 ↔ IPv4 Converter — Convert between IPv4 and IPv6 (mapped/expanded/compressed) and extract embedded IPv4.
  • User Agent Parser — Parse a User-Agent string into browser, engine, operating system and device, in your browser.
  • HAR File Viewer — Open a HAR file and inspect the request waterfall, headers, timings and sizes, in your browser.
  • IP Range to CIDR — Convert a start and end IP address into the minimal set of CIDR blocks, and back.
  • Set-Cookie Parser — Parse Set-Cookie and Cookie headers into a readable table of names, values and attributes.
  • IP Address to Integer Converter — Convert an IPv4 or IPv6 address to its integer, hex and binary form, and back.
  • MAC Address Generator — Generate random or vendor-prefixed MAC addresses in several formats.
  • WiFi QR Code Generator — Create a scannable QR code that joins a WiFi network, with correct escaping.
  • Download Time Calculator — Estimate how long a file takes to transfer at a given connection speed.
  • DMARC Record Generator — Build and validate a DMARC DNS TXT record with policy, reporting and alignment.
  • SPF Record Generator — Build and validate the SPF TXT record that stops others sending mail as your domain.
  • Port Number Lookup — What runs on a TCP or UDP port — search by number or service name.
  • Data Usage Calculator — Turn streaming, browsing and call habits into monthly gigabytes and cap forecasts.
  • DKIM Record Generator — Build and inspect the DKIM TXT record that publishes your mail signing key.
  • MTU & MSS Calculator — Work out TCP MSS from an MTU, allowing for IPv6, tunnels and TCP options.
  • Reverse DNS Generator — Turn IPs and prefixes into PTR names, zone files and RFC 2317 delegations.
  • CAA Record Generator — Build the DNS record that names which certificate authorities may issue for your domain.
  • SRV Record Generator — Build and decode SRV records for SIP, XMPP, Minecraft, LDAP and Autodiscover.
  • WHOIS Record Parser — Turn a raw WHOIS response into dates, registrar, name servers and decoded status codes.
  • Subnet Splitter — Split a CIDR block into equal subnets or size them by host count with VLSM.
  • DNS TXT Record Splitter — Split a long TXT value into 255-byte strings for DKIM, SPF and verification.
  • P2P File Transfer — Send files straight from one browser to another over a direct connection.
  • Email Domain Health Check — Paste your MX, SPF, DKIM and DMARC records for a scored deliverability report with fixes.

Guides

  • CIDR Notation and Subnetting, Explained — What CIDR notation like /24 means, how to find the subnet mask, network and broadcast address and usable hosts, plus private ranges and how to split a network.

Frequently asked questions

What can I do with these network tools?
Plan IP address space with the subnet and CIDR tools, the IPv6 ↔ IPv4 Converter and the IP Address to Integer Converter, build and check DNS records for mail, certificates and services, and read HAR captures, cookie headers, User-Agent strings and raw WHOIS responses. Smaller utilities look up ports, generate MAC addresses and work out MSS, download times and monthly data use, while the WiFi QR Code Generator and P2P File Transfer take care of sharing a network or a file.
How do I work out subnets for a network?
Enter a block such as 192.168.10.0/24 in the CIDR / Subnet Calculator to see its network and broadcast addresses, netmask and usable host range. To divide it, the Subnet Splitter splits by prefix, by subnet count or by the number of hosts each subnet must hold (VLSM) and exports the plan as CSV. IP Range to CIDR goes the other way, turning a start and end address into the smallest set of CIDR blocks for a firewall rule or route table.
Which DNS records can I build with these tools?
SPF, DKIM and DMARC records for email authentication, CAA records that limit which certificate authorities may issue for your domain, SRV records for services such as SIP, XMPP and Minecraft, and PTR records and zone files from the Reverse DNS Generator. The SPF, DKIM, DMARC, CAA and SRV generators can also check or explain an existing record you paste in, and the DNS TXT Record Splitter cuts long values such as DKIM keys into 255-byte strings. You then publish the result at your DNS provider.
Do these network tools send my data anywhere?
All but one keep your data on your device: addresses, keys, HAR captures and WiFi passwords are processed in your browser and never uploaded. P2P File Transfer is the exception by design. It sends files directly to the other person's browser over an encrypted connection and contacts a public STUN server only to learn the public address each device needs to connect, a lookup its same-Wi-Fi mode skips; ArrayKit never receives the files.
Can these tools ping a host, scan ports or query live DNS?
No. Apart from P2P File Transfer, which connects two browsers, they work only on what you type, paste or open and send no probes or DNS queries. Port Number Lookup searches a built-in table, the WHOIS Record Parser reads a response you copied, and the record generators check syntax and limits such as the SPF cap of 10 DNS lookups. To see what is live, the CAA Record Generator and SRV Record Generator give you a dig command, and the MTU & MSS Calculator gives you the ping command to run yourself.