An administrator connects a server to an external gigabit switch, but the server can only...

Comprehensive Detailed Explanation with all CompTIA Server+ SK0-005 Study Guide References:The most likely cause of a speed mismatch (100Mbps instead of 1Gbps) is a defective or incompatible network cable. Gigabit Ethernet requires at least Cat5e or Cat6 cables; using older cables (e.g., Cat5) or damaged cables can limit speeds to 100Mbps.

Port securityandVLAN misconfigurationwould typically prevent communication entirely, not reduce speed.

Incorrect IP subnetdoes not affect link speed.Checking and replacing the network cable is a logical first troubleshooting step in this scenario.