A systems administrator is investigating a performance problem with a newly racked physical server. Although the server responds to ping, large file transfers crawl and application sessions frequently time out. The network switch port connected to the server is hard-coded to 100 Mbps, full-duplex. In the server's operating system the NIC statistics show a rapidly increasing number of CRC errors and collisions.
Which of the following is the MOST likely cause of the issue?
The server is connected with a faulty patch cable.
The server's NIC is set to auto-negotiate speed and duplex.
The server has been configured with incorrect IP address settings.
The network switch port is experiencing a hardware failure.
The server NIC is still configured for auto-negotiation. When one side of an Ethernet link is manually set to a fixed speed and duplex (100 Mb/s full) and the other side remains on auto-negotiation, the auto-negotiating device cannot determine the duplex mode. Per IEEE 802.3, it therefore defaults to half-duplex, creating a duplex mismatch. The half-duplex side detects many collisions, the full-duplex side records FCS/CRC errors, and bulk traffic slows dramatically even though basic connectivity (ping) still works.
Why the other choices are wrong:
A faulty patch cable can cause CRC errors, but it does not normally generate high collision counts, the hallmark of a duplex mismatch.
Incorrect IP settings would prevent or limit connectivity rather than merely slow large transfers while leaving Layer-2 error counters climbing.
A switch-port hardware failure is more likely to drop the link entirely or flap the interface than to show consistent collision/CRC patterns.