CompTIA Network+ (N10-009)Network TroubleshootingMedium
A technician is troubleshooting a server that connects to a 10Gbps switch port. Performance monitoring shows that the server's network interface is consistently operating at 1Gbps, despite the NIC being a 10Gbps card and the switch port configured for 10Gbps. The cable used is a Cat 6a, rated for 10Gbps up to 100 meters. Which of the following is the MOST probable cause of the speed discrepancy?
- AA faulty Cat 6a cable.
- BThe server's operating system is not optimized for 10Gbps.
- CThe switch port is configured for half-duplex.
- DThe server's TCP window size is too small.
Show answer & explanationAnswer & explanation
Correct answer: A. A faulty Cat 6a cable.
Even with a Cat 6a cable, if there's any damage, improper termination, or excessive length/interference, it might auto-negotiate down to the highest reliable speed it can achieve, which is often 1Gbps. Since both the NIC and switch are capable of 10Gbps and configured for it, a faulty cable is the most probable physical layer cause for the negotiation down to 1Gbps.
Why the other options are wrong
- B. While OS optimization can affect throughput, it's unlikely to cause a hard negotiation down to 1Gbps when 10Gbps is available at the physical layer.
- C. Half-duplex would cause severe performance issues and collisions but wouldn't necessarily force a speed negotiation down to 1Gbps if 10Gbps full-duplex is otherwise viable.
- D. TCP window size affects application-layer throughput but does not dictate the negotiated link speed at the physical layer.
Link Speed Auto-negotiation Failure
Occurs when two connected network devices fail to agree on the highest common supported speed and duplex mode, often defaulting to a lower speed or half-duplex.
- Can be caused by faulty cables, incompatible hardware, or misconfigured ports.
- Results in reduced throughput and performance issues.
- Troubleshoot by checking cables, port settings, and device compatibility.
Memory trick: Speed mismatch? Check the 'chain' for a weak link.