CompTIA Tech+ (FC0-U71)InfrastructureHard
A system administrator is tasked with connecting a legacy server to a modern network switch. The server has an older network interface card (NIC) that only supports a maximum speed of 100 Mbps, while the new switch ports operate at 1000 Mbps. To ensure reliable communication, what is the MOST important configuration setting that MUST be correctly set on both the server's NIC and the switch port?
- AIP address
- BJumbo frames
- CVLAN tag
- DDuplex mode
Show answer & explanationAnswer & explanation
Correct answer: D. Duplex mode
When devices with different speeds are connected, auto-negotiation should ideally handle both speed and duplex. However, if auto-negotiation fails or is manually overridden, a mismatch in duplex mode (e.g., one side is half-duplex and the other is full-duplex) between the NIC and the switch port will cause severe performance issues, collisions, and intermittent connectivity, even if the speed negotiates correctly.
Why the other options are wrong
- A. An incorrect IP address would prevent network communication entirely, but a duplex mismatch can cause partial or unreliable communication, which is more insidious to troubleshoot.
- B. Jumbo frames are an optimization for larger data packets and are not a fundamental requirement for basic reliable communication between devices of different speeds; an incorrect setting would cause packet drops, not fundamental link issues.
- C. VLAN tags are for network segmentation and do not directly impact the physical layer communication speed or duplex mode.
Ethernet Duplex Mismatch
A configuration error where two connected Ethernet devices are set to different duplex modes (e.g., one is full-duplex, the other is half-duplex), leading to severe network performance issues and high collision rates.
- Full-duplex allows simultaneous send/receive; half-duplex allows one at a time.
- Mismatches cause collisions and retransmissions.
- Results in significantly reduced throughput and intermittent connectivity.
- Auto-negotiation usually prevents this, but manual misconfiguration can cause it.
Memory trick: Duplex mismatch: A traffic jam of communication.