CompTIA Server+ (SK0-005)TroubleshootingMedium
A system administrator is troubleshooting a server that is experiencing intermittent network connectivity issues. After checking the physical connections and confirming the NIC is recognized by the OS, they notice high error rates reported by the network interface statistics, specifically an increasing number of 'late collisions'. Which of the following is the MOST likely cause of this issue?
- AThe server's firewall is blocking legitimate network traffic.
- BIncorrect subnet mask configuration on the server.
- CA duplex mismatch between the server's NIC and the switch port.
- DInsufficient bandwidth allocated to the server's network connection.
Show answer & explanationAnswer & explanation
Correct answer: C. A duplex mismatch between the server's NIC and the switch port.
Late collisions are a strong indicator of a duplex mismatch, especially in older or misconfigured Ethernet environments. When one side is full-duplex and the other is half-duplex, the half-duplex side may transmit while the full-duplex side is also transmitting, leading to collisions that are detected 'late' by the half-duplex device.
Why the other options are wrong
- A. A firewall blocking traffic would manifest as unreachable services, not network layer collision errors.
- B. An incorrect subnet mask would cause routing issues, not typically late collisions.
- D. Insufficient bandwidth would lead to congestion and dropped packets, not specifically late collisions.
Duplex Mismatch
A duplex mismatch occurs when two connected network devices (e.g., a server NIC and a switch port) are configured with different duplex settings (one full-duplex, one half-duplex).
- Leads to severe performance degradation and high error rates.
- Commonly causes late collisions on half-duplex side.
- Often results in retransmissions and slow network speeds.
Memory trick: Duplex drama: half vs. full, a network duel.