N10-009 Question 190
Single answerDocumentation: Physical vs. logical diagrams, Rack diagrams, Cable maps and diagrams, Network diagrams (Layer 1, Layer 2, Layer 3)A network administrator is troubleshooting a connectivity issue after a branch office move. Users can reach devices on their local VLAN, but they cannot access resources in other subnets. The administrator has already confirmed that all patch cables are connected correctly in the closet and that the switch stack is powered on. To most efficiently verify whether the routed VLAN interfaces, subnet assignments, and inter-VLAN paths were documented correctly, which type of documentation should the administrator review first?
- A
Layer 3 network diagram
- B
Rack diagram
- C
Cable map/diagram
- D
Physical topology diagram
Show answer and explanation
Correct answer: A
Explanation
This scenario distinguishes physical connectivity documentation from logical/routed documentation. Because users can communicate within their local VLAN, Layer 1 and likely Layer 2 connectivity are functioning. The failure occurs when traffic needs to move between subnets, which is a Layer 3 function. A Layer 3 network diagram is the best first reference because it should document routed VLAN interfaces, IP addressing, default gateway assignments, and network paths between subnets. By contrast, rack diagrams help locate equipment, cable maps document physical cabling and port mappings, and physical topology diagrams show device interconnections without necessarily including routing details. In Network+ troubleshooting, choosing the correct documentation type helps reduce time spent checking areas that do not match the symptoms.
- A. Correct.
Correct. A Layer 3 network diagram documents routed connections, IP subnets, VLAN interface addressing, gateway relationships, and paths between networks. Because the issue affects communication between subnets rather than local connectivity within a VLAN, this is the most relevant documentation to review first.
- B. Incorrect.
Incorrect. A rack diagram shows the physical placement of equipment in racks, such as which switch, patch panel, or router occupies a given rack unit. This is useful for locating hardware during installation or maintenance, but it does not typically document subnet assignments or routing relationships between VLANs.
- C. Incorrect.
Incorrect. A cable map or cable diagram focuses on physical cable runs, terminations, and port-to-port connectivity. Since the administrator has already confirmed that patch cables are connected and local VLAN access works, the problem is less likely to be caused by a cabling issue and more likely related to Layer 3 configuration or documentation.
- D. Incorrect.
Incorrect. A physical topology diagram shows how devices are physically connected, such as switches uplinked to routers or firewalls. While this can help identify major interconnections, it usually does not provide the detailed routed interface, subnet, and inter-VLAN information needed to verify communication between different subnets.