Reference Sheets
Quick-access reference material for IT certification exams. Search, filter, and print any sheet.
Port Numbers
Common TCP/UDP ports for networking exams — sortable by port number, protocol, or service name.
OSI Model
All 7 layers with protocols, PDUs, devices, and a memory aid to lock it in.
Linux Commands
Essential Linux commands organized by category — file management, networking, permissions, and more.
Cryptography
Symmetric, asymmetric, and hashing algorithms compared side by side with key sizes and use cases.
Subnetting
CIDR table from /8 to /32 with subnet masks, host counts, and wildcard masks.
Acronyms
A-Z glossary of IT acronyms commonly seen on CompTIA, AWS, and other certification exams.