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 has been configured with incorrect IP address settings.
The server is connected with a faulty patch cable.
The server's NIC is set to auto-negotiate speed and duplex.
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.