A user with a home office wants to add additional devices to the existing internet...

To add additional wired network devices in a simple and cost-effective manner, the best solution is an unmanaged switch. CompTIA A+ explains that unmanaged switches require no configuration, provide instant port expansion, and operate using plug-and-play functionality. This makes them ideal for home offices where the user wants more Ethernet ports without dealing with administrative overhead or complex setup.

An unmanaged switch automatically forwards traffic using MAC addresses, expanding the network without altering IP configuration or security settings. It is inexpensive compared to other networking equipment and requires no firmware updates, VLAN management, or routing knowledge.

A DSL modem or cable modem provides internet service but does not increase the number of available network ports beyond the single LAN port commonly offered. A firewall controls traffic but does not expand physical connectivity. Therefore, neither modem nor firewall options meet the requirement of adding more wired devices.

Thus, the unmanaged switch is the simplest, cheapest, and most practical choice for expanding connectivity in a home office environment.