N10-009 Question #223: Real Exam Question with Answer & Explanation

Question

A virtual machine has the following configuration: - IPv4 address: 169.254.10.10 - Subnet mask: 255.255.0.0 The virtual machine can reach collocated systems but cannot reach external addresses on the internet. Which of the following is most likely the root cause?

Options

• AThe subnet mask is incorrect.
• BThe DHCP server is offline.
• CThe IP address is an RFC1918 private address.
• DThe DNS server is unreachable.

Explanation

The virtual machine's 169.254.10.10 IP address indicates it has self-assigned an APIPA address, which occurs when a DHCP server is unavailable to provide a proper IP configuration, preventing internet access.

Common mistakes.

• A. The subnet mask 255.255.0.0 is the correct and standard subnet mask for an APIPA address in the 169.254.0.0/16 range, so it is not the root cause of the internet connectivity issue.
• C. While 169.254.x.x addresses are non-routable private addresses, they are specifically APIPA addresses, not RFC1918 private addresses (which are 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16); the underlying issue is the failure to obtain a proper IP configuration, likely due to a DHCP server being offline.
• D. An unreachable DNS server would prevent hostname resolution, but the virtual machine would still be able to connect to external addresses if contacted via their IP address; the problem describes a failure to reach external addresses in general, indicating a lack of routing to the internet.

Concept tested. APIPA addressing and DHCP issues

Reference. https://learn.microsoft.com/en-us/troubleshoot/windows-server/networking/understanding-apipa-addressing

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