IT tool
IPv4 Subnet Calculator
Network and broadcast addresses, usable host range, wildcard and binary masks for any IPv4 address and prefix, with correct /31 and /32 handling and a subnet split helper.
Free calculators & utilities
IT Tools
Small, fast utilities for everyday network and systems work. Each one runs entirely in your browser: what you type isn't sent to this site or anyone else, isn't saved, and isn't added to the page address. Your browser's own features, such as form autofill and extensions, are outside this site's control. On a shared computer, clear anything sensitive before you walk away.
For step-by-step guides and printable references, browse the Resource Center.
Calculators and utilities
IT tool
Cisco Type 7 Password Decoder
Recover a Type 7 password from a configuration you manage. Type 7 is reversible obfuscation, not encryption. Read the warning before you use it.
IT tool
Wildcard Mask Calculator for Cisco ACLs
Convert a subnet mask or prefix to a Cisco wildcard mask, or check any ACL address and wildcard, including noncontiguous ones, and test which addresses it matches.
IT tool
Mental Subnetting Trainer
Practice subnetting without a chart: enter an IPv4 address and prefix, then reveal the interesting octet, increment, block, network, broadcast and usable range one step at a time, or test yourself on random questions.
Curated external resources
Other sites worth knowing, each with a review on this site. They aren't run by Ellington Technologies.
External site Remote Support / Visual Troubleshooting
Chasms.com
Reference versions of common operating systems, browsers, email apps and modems to look at while you talk someone through a fix by phone.
For how the IT Resource Center is researched, reviewed and corrected, see How These Guides Are Made.