101 · Question #650
An administrator is having a connectivity issue with a server in the same network. Upon checking with the command arp -a on a Windows machine, the two outputs are taken on a 1 minute interval. What is
The correct answer is D. IP address conflict. When the ARP table shows a different MAC address for the same IP across two captures taken one minute apart, the defining cause is an IP address conflict where two devices share the same IP.
Question
An administrator is having a connectivity issue with a server in the same network. Upon checking with the command arp -a on a Windows machine, the two outputs are taken on a 1 minute interval. What is likely causing this issue?
Exhibit
Options
- AInterface down
- BMAC address conflict
- CNo route available
- DIP address conflict
How the community answered
(22 responses)- A5% (1)
- B5% (1)
- C9% (2)
- D82% (18)
Why each option
When the ARP table shows a different MAC address for the same IP across two captures taken one minute apart, the defining cause is an IP address conflict where two devices share the same IP.
A down interface would remove the ARP entry entirely rather than produce a changing entry, because no ARP replies would be received.
A MAC address conflict involves two interfaces sharing the same MAC, which would not cause the ARP table to show two different MACs resolving to the same IP.
A missing route is a Layer 3 issue and does not affect ARP, which operates at Layer 2 and resolves IPs to MACs within the local segment.
An IP address conflict causes two separate devices to respond to ARP requests for the same IP, each advertising their own MAC address. Running arp -a at one-minute intervals will show the MAC address for that IP alternating between the two conflicting devices, which is the textbook symptom of a duplicate IP assignment and explains the connectivity instability.
Concept tested: IP address conflict detection via ARP table comparison
Source: https://learn.microsoft.com/en-us/troubleshoot/windows-server/networking/duplicate-ip-address-conflicts-on-network
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