Cheat Sheet
Cisco CCNA (200-301) Cheat Sheet
By The Exam Atlas Editorial Team · Verified 2026-05-29
A final-revision summary for CCNA 200-301. Study aid only — no notes in the proctored exam.
Subnetting quick reference (IPv4)
| CIDR | Mask | Hosts |
|---|
| /24 | 255.255.255.0 | 254 |
| /25 | 255.255.255.128 | 126 |
| /26 | 255.255.255.192 | 62 |
| /27 | 255.255.255.224 | 30 |
| /28 | 255.255.255.240 | 14 |
| /30 | 255.255.255.252 | 2 (point-to-point) |
OSI layers (top to bottom)
Application · Presentation · Session · Transport · Network · Data Link · Physical.
Common ports
| Port | Service |
|---|
| 22 / 23 | SSH / Telnet |
| 53 | DNS |
| 67/68 | DHCP |
| 80 / 443 | HTTP / HTTPS |
| 123 | NTP |
| 161/162 | SNMP |
Key protocols and terms
| Term | Idea |
|---|
| VLAN / 802.1Q | Segmenting a switched network / trunk tagging |
| STP | Prevents switching loops |
| OSPF | Link-state routing protocol |
| NAT / PAT | Translating private to public addresses |
| ACL | Filtering traffic by rules |
| EtherChannel | Bundling links for bandwidth and redundancy |
FAQ
- Can I use notes in the CCNA exam?
- No. It is proctored. Use this for final revision before exam day only.
Sources
