Networking Basics
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Subnetting, CIDR, private IP ranges, and the TCP/IP foundations every Network+ candidate needs cold.
Mnemonic
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Full OSI Model Explainer
All 7 layers in depth — what each does, which protocols live there, encapsulation diagrams, devices by layer, and common troubleshooting approaches.
Open OSI Model →
Formula
Usable hosts = 2^(32 − prefix) − 2
Subtract 2 for the network address and broadcast address. Exception: /31 and /32 used in point-to-point and host routes.
| CIDR |
Subnet Mask |
Wildcard Mask |
Usable Hosts |
Notes |
| Range |
CIDR |
Total Addresses |
RFC |
Purpose |