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CCNA Network Infrastructure and Connectivity Practice Question
Drag and drop the following troubleshooting steps into the correct order to diagnose a client connectivity issue using the OSI bottom-up method.
⚠ Common exam trap
The exam trap is that candidates may confuse bottom-up with top-down troubleshooting or think that checking the network layer first is more efficient. Remember: bottom-up always starts at the physical layer and proceeds sequentially upward.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Check physical connectivity, then data link, then network, then transport, then application
The OSI bottom-up method starts at physical layer and moves up. This ensures that lower-layer issues are resolved before higher-layer troubleshooting, preventing wasted effort on symptoms caused by underlying problems.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Check physical connectivity, then data link, then network, then transport, then application
Why this is correct
The bottom-up approach enforces a strict Layer 1 → Layer 4 progression: verify cable integrity, interface status, and link lights first, then check Layer 2 framing, MAC addressing, and VLAN membership, followed by Layer 3 IP addressing and routing, Layer 4 TCP/UDP ports and sessions, and finally application-level behavior. This ordering prevents wasted effort debugging upper-layer issues that are actually caused by a downed physical link. It is the methodical, citable sequence in Cisco troubleshooting methodology.
- ✗
Check application, then transport, then network, then data link, then physical
Why it's wrong here
This sequence reverses the OSI model from top to bottom, so it is a top-down strategy rather than the bottom-up approach required. Starting with application-layer checks first assumes the lower layers are healthy, but a silent physical or data link failure will make application symptoms appear, leading to numerous false leads. In a strict bottom-up context, this order is incorrect because it does not establish the network foundation before layer 7.
- ✗
Check network, then data link, then physical, then transport, then application
Why it's wrong here
This ordering begins at Layer 3, drops abruptly to Layer 2, then Layer 1, and then jumps back up to Layers 4 and 5, violating the incremental layer-by-layer progression. A proper bottom-up method never revisits a lower layer after moving to a higher layer, because each upper layer depends on all layers beneath it. Checking network before data link is valid only if Layer 2 has been verified, but here it is checked after, so the sequence cannot isolate faults reliably.
- ✗
Check physical, then network, then data link, then transport, then application
Why it's wrong here
Although this sequence correctly starts at the physical layer, its next step jumps straight to Layer 3 networking without first validating Layer 2 switching and framing. In a bottom-up approach, the data link layer must be checked immediately after Layer 1 because Ethernet frames, MAC tables, and switch interfaces depend on a functioning physical link; routing and IP addressing cannot be meaningfully tested if Layer 2 is broken. This omission makes the order incorrect despite having the right initial layer.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓Check physical connectivity, then data link, then network, then transport, then applicationCorrect answer▾
Why this is correct
The bottom-up approach enforces a strict Layer 1 → Layer 4 progression: verify cable integrity, interface status, and link lights first, then check Layer 2 framing, MAC addressing, and VLAN membership, followed by Layer 3 IP addressing and routing, Layer 4 TCP/UDP ports and sessions, and finally application-level behavior. This ordering prevents wasted effort debugging upper-layer issues that are actually caused by a downed physical link. It is the methodical, citable sequence in Cisco troubleshooting methodology.
✗Check application, then transport, then network, then data link, then physicalWrong answer — click to see why▾
Why this is wrong here
The order is reversed; bottom-up starts at the physical layer, not the application layer.
Why candidates choose this
Candidates might confuse bottom-up with top-down troubleshooting, especially if they are more familiar with application-layer issues.
✗Check network, then data link, then physical, then transport, then applicationWrong answer — click to see why▾
Why this is wrong here
A true bottom-up approach must start at the physical layer and proceed sequentially upward without skipping or reordering.
Why candidates choose this
Candidates might think that checking the network layer first is efficient because it is often the source of connectivity issues, but this violates the bottom-up methodology.
✗Check physical, then network, then data link, then transport, then applicationWrong answer — click to see why▾
Why this is wrong here
The OSI model layers must be checked in order: physical, data link, network, transport, session, presentation, application. Skipping data link after physical is a common mistake.
Why candidates choose this
Candidates might overlook the data link layer because they focus on IP (network layer) issues, but bottom-up requires checking each layer sequentially.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Visual reference
Quick reference
OSI Model Reference
| Layer | Name | PDU | Key Protocols / Devices |
|---|---|---|---|
| 7 | Application | Data | HTTP, HTTPS, DNS, SMTP, FTP, SSH |
| 6 | Presentation | Data | TLS / SSL, JPEG, ASCII encoding |
| 5 | Session | Data | NetBIOS, RPC, SIP |
| 4 | Transport | Segment / Datagram | TCP, UDP |
| 3 | Network | Packet | IP, ICMP, OSPF — Routers |
| 2 | Data Link | Frame | Ethernet, Wi-Fi, PPP — Switches, Bridges |
| 1 | Physical | Bits | Cables, NICs, Hubs, Repeaters |
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.