Exam facts at a glance
- ~100-120 questions, multiple choice, drag-and-drop, and simulation-style items.
- 120 minutes.
- $300 USD per attempt.
- Passing score: not published; ~825/1000 (scaled) is the widely cited figure.
- Valid 3 years.
- Retake wait: 5 / 30 / 45 / 180 calendar days, escalating with each failed attempt.
- Pearson VUE test center or Pearson OnVUE online. Closed book.
- Full exam-format details: CCNA Exam Guide 2026.
Subnetting quick reference
The single most-tested skill embedded across every domain. Usable hosts per subnet = 2^(host bits) − 2.
| CIDR | Subnet Mask | Usable 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 |
| /29 | 255.255.255.248 | 6 |
| /30 | 255.255.255.252 | 2 |
Exam tell: "at least N usable hosts, fewest wasted addresses" → find the smallest subnet size whose usable-host count still meets N. Full walkthrough: Subnetting Explained.
OSI model at a glance
| Layer | Name | Example |
|---|---|---|
| 7 | Application | HTTP, DNS, DHCP |
| 6 | Presentation | Encryption, encoding |
| 5 | Session | Session establishment |
| 4 | Transport | TCP, UDP, port numbers |
| 3 | Network | IP addressing, routing |
| 2 | Data Link | MAC addressing, switching |
| 1 | Physical | Cabling, signaling |
Administrative distance table
Lower administrative distance always wins when multiple sources offer a route to the same destination — checked before metric.
| Source | Default AD |
|---|---|
| Directly connected | 0 |
| Static route | 1 |
| EIGRP (internal) | 90 |
| OSPF | 110 |
| RIP | 120 |
| Unknown / unreachable | 255 (never installed) |
STP port states and roles
- Root port: the one port per non-root switch with the best path back to the root bridge.
- Designated port: the forwarding port on each network segment, chosen for the best path to the root.
- Blocking port: discards data frames to prevent a loop, but still listens for BPDUs.
- Root bridge election: lowest Bridge ID wins (priority, then MAC address as tiebreaker).
OSPF vs EIGRP at a glance
| Property | OSPF | EIGRP |
|---|---|---|
| Type | Open standard, link-state | Cisco-proprietary, advanced distance-vector |
| Metric | Cost (based on bandwidth) | Composite (bandwidth + delay by default) |
| Admin distance | 110 | 90 (internal) |
| Convergence | Fast (SPF recalculation) | Very fast (DUAL, feasible successors) |
| CCNA depth required | Deep — primary routing protocol on the exam | Conceptual awareness only |
OSPF is the routing protocol CCNA actually configures and troubleshoots in depth. Full breakdown: OSPF Explained.
NAT types
- Static NAT: one-to-one, permanent mapping of a private address to a public address.
- Dynamic NAT: maps private addresses to a pool of public addresses, first-come-first-served.
- PAT (NAT overload): many private addresses share one public address, distinguished by port number — the most common real-world NAT type.
ACL types
- Standard ACL: filters by source IP address only. Numbered 1-99 or 1300-1999.
- Extended ACL: filters by source/destination IP, protocol, and port. Numbered 100-199 or 2000-2699.
- Placement rule: place standard ACLs close to the destination (they can only match source, so placing them near the source over-blocks). Place extended ACLs close to the source (they can match precisely, so blocking early saves bandwidth).
Wireless standards and security
- 802.11ac / 802.11ax (Wi-Fi 6): current-generation standards tested at a conceptual level — frequency bands (2.4 GHz vs 5 GHz) and non-overlapping channels.
- WPA2: AES encryption, still widely deployed.
- WPA3: current-generation standard, stronger encryption and protection against offline password-guessing attacks.
Automation vocabulary
- REST API: the standard way modern network devices and controllers expose programmatic configuration and monitoring.
- JSON: the standard data format for REST API request/response bodies.
- SDN (Software-Defined Networking): separates the control plane (decision-making) from the data plane (forwarding), typically centralized in a controller.
- Ansible / Puppet / Chef: configuration-management tools that automate device configuration at scale — know them by name and purpose, not syntax, for CCNA.
Common port numbers
| Protocol | Port |
|---|---|
| DNS | 53 |
| DHCP (server/client) | 67 / 68 |
| HTTP / HTTPS | 80 / 443 |
| SSH | 22 |
| Telnet | 23 |
| SNMP | 161 |
| NTP | 123 |
show command quick reference
The commands you actually run inside a simlet to diagnose what is broken before touching any configuration. Run these first, every time.
| Command | What it reveals |
|---|---|
show ip route | The routing table: which routes are installed, their source (connected/static/OSPF), and administrative distance/metric. |
show ip interface brief | Interface status/protocol state (up/up, up/down, admin down) and assigned IP addresses at a glance — the fastest first-look command on any device. |
show vlan brief | VLAN-to-port assignments and which VLANs exist on the switch — confirms a port is actually in the VLAN you expect. |
show interfaces trunk | Trunk ports, their native VLAN, and the allowed-VLAN list — the command that exposes a native VLAN mismatch or a VLAN missing from the allowed list. |
show ip ospf neighbor | OSPF adjacency state per neighbor (Full, 2-Way, INIT, EXSTART/EXCHANGE) — the state tells you the likely fault category before you dig further. |
show ip protocols | Which routing protocol is running, its configured networks, and administrative distance — confirms OSPF is actually enabled on the interfaces you think it is. |
show spanning-tree | Root bridge, port roles (root/designated/blocking), and STP state per port — confirms whether a port is blocking traffic as designed or unexpectedly. |
show mac address-table | Learned MAC-to-port mappings — useful for confirming a switch actually sees traffic from a device where you expect it. |
show access-lists | ACL entries and per-line match counters — shows whether an ACL is actually matching the traffic you think it should be blocking or permitting. |
show running-config | The full active configuration — the ground truth when a show summary command does not explain the symptom on its own. |
Configuration command quick reference
The commands you type to build or fix a scenario, grouped by the four configuration areas simlets test most.
| Task | Command(s) |
|---|---|
| Create a VLAN | vlan 10 then name SALES |
| Assign an access port to a VLAN | interface fa0/1, switchport mode access, switchport access vlan 10 |
| Configure a trunk port | switchport mode trunk, switchport trunk native vlan 99, switchport trunk allowed vlan 10,20,30 |
| Enable OSPF and advertise a network | router ospf 1 then network 10.0.0.0 0.0.0.255 area 0 — the second value is a wildcard mask, not a subnet mask. |
| Set an OSPF router ID | router-id 1.1.1.1 (inside router ospf config mode) |
| Standard ACL: block one host | access-list 10 deny host 192.168.1.5 then access-list 10 permit any |
| Extended ACL: block one protocol/port | access-list 100 deny tcp host 192.168.1.5 any eq 23 then access-list 100 permit ip any any |
| Apply an ACL to an interface | interface g0/0 then ip access-group 100 in |
| Configure PAT (NAT overload) | ip nat inside source list 1 interface g0/1 overload, plus ip nat inside / ip nat outside on the relevant interfaces |
Exam tell: the OSPF network statement wildcard mask is the inverse of a subnet mask (a /24 is 0.0.0.255, not 255.255.255.0) — this single mix-up is one of the most common configuration-command mistakes on simlets.
Abbreviations glossary
| Abbreviation | Meaning |
|---|---|
| VLSM | Variable Length Subnet Masking — subnetting a network into unequal-sized pieces to minimize wasted addresses. |
| STP | Spanning Tree Protocol — prevents Layer 2 loops by blocking redundant paths. |
| BPDU | Bridge Protocol Data Unit — the message switches exchange to run STP and elect the root bridge. |
| DUAL | Diffusing Update Algorithm — the algorithm EIGRP uses to guarantee loop-free, fast convergence via feasible successors. |
| SPF | Shortest Path First — the Dijkstra-based algorithm OSPF uses to calculate best routes from its link-state database. |
| ACL | Access Control List — a rule set that permits or denies traffic based on address, protocol, or port. |
| NAT / PAT | Network Address Translation / Port Address Translation — translating private addresses to public ones, PAT specifically via shared address + port. |
| ARP | Address Resolution Protocol — resolves an IPv4 address to a MAC address on the local segment. |
| DHCP / DORA | Dynamic Host Configuration Protocol / Discover-Offer-Request-Acknowledge — the four-message process a client uses to lease an IP address. |
| OSPF / EIGRP | Open Shortest Path First / Enhanced Interior Gateway Routing Protocol — the two interior routing protocols tested on CCNA, OSPF in depth. |
| AAA | Authentication, Authorization, Accounting — the framework for verifying identity, controlling access, and logging activity. |
| SDN | Software-Defined Networking — separates the control plane from the data plane, typically centralized in a controller. |
| QoS | Quality of Service — prioritizes certain traffic (like voice) over others when bandwidth is constrained. |
| MTU | Maximum Transmission Unit — the largest frame size an interface will forward; a mismatch between neighbors can block OSPF adjacency formation. |
| FHRP / HSRP | First Hop Redundancy Protocol / Hot Standby Router Protocol — provides a redundant default gateway if the primary router fails. |
Top 5 trap-question patterns
- "Which route is installed?" — always compare administrative distance first, metric only within the same source.
- Standard ACL for protocol/port filtering — wrong. Standard ACLs only match source IP; use extended for protocol or port.
- Access port carrying multiple VLANs — always wrong. Access ports carry exactly one VLAN; trunk ports carry multiple.
- Confusing OSPF cost with EIGRP composite metric — OSPF cost is bandwidth-based; EIGRP’s default metric factors in both bandwidth and delay.
- Reading "select TWO" as "select the best ONE" — multiple-response items require every correct option; there is no partial credit.
Detailed explanations in How to Pass CCNA on the First Try.
Exam-day pocket guide
- ~100-120 questions, 120 minutes. Simlets can take 5-8 minutes each — budget accordingly and do not panic if the clock feels tight mid-exam.
- "Select TWO/THREE" questions: read the stem twice, no partial credit.
- Directly connected beats static beats EIGRP beats OSPF beats RIP, by administrative distance, whenever routes to the same destination compete.
- Extended ACLs go near the source; standard ACLs go near the destination.
- In a simlet, run
showcommands first to understand the actual topology state before answering — do not assume the diagram matches a healthy configuration. - Passing score is unpublished and scaled — do not try to count your correct answers during the exam.
- If frozen on a question past 2 minutes: flag, move on, return at the end.
Frequently asked questions
Can I use this cheat sheet during the CCNA exam?
No. 200-301 is closed book under proctored conditions, whether you sit it at a Pearson VUE test center or online via Pearson OnVUE — you cannot bring notes, a printed reference, a second monitor, or any external material into the exam session itself, and OnVUE's pre-exam room scan is specifically designed to catch anything like this on your desk. Use this cheat sheet as a review and memorization tool before the exam, not as something to consult mid-exam. The most effective way to use it is to read it end-to-end once early in your study period to preview scope, reference individual sections as you cover each domain in depth, and then read it again in full during the final 48-72 hours before your exam date, once you no longer need to look anything up and are simply reinforcing what you already know cold.
Is there a printable PDF of the CCNA cheat sheet?
A dedicated printable PDF version is coming soon. For now, the most reliable way to get a clean offline copy is your browser's built-in print function (Ctrl+P on Windows, Cmd+P on Mac) with the destination set to "save as PDF" rather than a physical printer — this preserves the tables and formatting far better than copying the text into a separate document. Many candidates print this page during their final week of study and keep it as a physical or digital reference alongside their Packet Tracer lab notes, since flipping between browser tabs while running simulations is slower than glancing at a printed page. Just remember that whatever you print is for pre-exam review only — none of it can accompany you into the actual proctored exam session at a test center or via OnVUE. A printed copy stored alongside your Packet Tracer lab files also makes a convenient single reference point during your final review week.
What is the single most important section to memorize?
The subnetting quick reference and the administrative distance table, in that order. Slow subnetting math and confusing which routing source wins when multiple sources offer a route to the same destination account for the largest share of missed points among first-time CCNA candidates, and both show up embedded inside questions from domains that are not explicitly "about" them — a security or IP-services scenario can just as easily hide a subnetting calculation as a Network Fundamentals question can. The administrative distance table matters because "which route gets installed" questions test whether you compare administrative distance before metric, a rule that trips up candidates who assume the "better" protocol always wins rather than checking the fixed distance values first. If your study time before exam day is genuinely limited, drilling these two sections until they are automatic will move your score more than any other single hour of review.
Does this cheat sheet cover everything on the exam?
No, and it is not meant to. It covers the high-yield reference material — subnetting, routing preference, STP, OSPF versus EIGRP, NAT and ACL types, the show and configuration commands that come up most often in simlets, and the trap-question patterns that repeatedly catch first-time candidates. It is deliberately a compression for final review, not a substitute for hands-on Cisco Packet Tracer labs, a structured study plan, or the depth of the full CertSharp question bank. Candidates who try to learn CCNA from a cheat sheet alone, without ever building a topology or working through explanations on hundreds of practice questions, consistently struggle on the simulation-style items regardless of how well they have memorized the reference tables here. Pair this page with real lab time and the full CertSharp CCNA question bank for a complete study plan, not as a replacement for either.
Pair the cheat sheet with practice
The cheat sheet is for review. The CertSharp question bank is for testing whether you have actually internalized it. 30 free questions, no signup. $11.99 lifetime for the full 500.