Newly Released CompTIA N10-009 Exam PDF

The customer can access local resources (a database server), which means local networking is working. However, the inability to reach the internet suggests an issue with the default gateway. If the default gateway is unreachable, packets will not be routed outside the local network.

Breakdown of Options:

A. Incorrect DNS – DNS issues would cause problems resolving domain names, but the user should still be able to access external resources via IP addresses.

B. Unreachable gateway – ✅ Correct answer. If the default gateway is incorrect or unreachable, the device cannot route traffic to the internet.

C. Failed root bridge – STP (Spanning Tree Protocol) failures cause switching issues, but the user can still access local devices, meaning STP is not the problem.

D. Poor upstream routing – Would affect the entire network, not just one user.

The CompTIA Troubleshooting Methodology states that after testing the theory, the next step is to establish a plan of action to resolve the issue.

Troubleshooting Steps:

Identify the problem.

Establish a theory of probable cause.

Test the theory to determine the cause.

Establish a plan of action and implement the solution. ✅ (Correct step)

Verify full system functionality.

Document findings, actions, and outcomes.

Breakdown of Options:

A. Verify full system functionality – Happens after implementing the solution.

B. Document the findings and outcomes – Final step, happens after resolving the issue.

C. Establish a plan of action – ✅ Correct answer. Comes immediately after confirming the cause.

D. Identify the problem – First step, already completed.

A /21 subnet mask means 21 bits are network bits:

8 + 8 + 5 = 21 → leaves 11 bits for hosts.

Subnet mask in binary: 11111111.11111111.11111000.00000000

Converted to decimal: 255.255.248.0

Therefore:

A. /19 = 255.255.224.0

B. /20 = 255.255.240.0

✅ C. /21 = 255.255.248.0 ← correct

D. /22 = 255.255.252.0

Answer correction: The correct option is C. 255.255.248.0, not B.

References (CompTIA Network+ N10-009):

Domain: Networking Concepts — Subnetting, CIDR notation, dotted decimal masks.

A TXT record can be used to store SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) information, which help verify that an email has been sent from a trusted source.

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