NICs

Network interface cards (NICs) are hardware devices that allow a computer or other device to connect to a network. They can be built into the motherboard, added as PCIe expansion cards, or supplied as USB adapters, and they may provide wired Ethernet or wireless connectivity. A NIC presents a network interface to the operating system and handles transmission and reception of data over the local network.

Most NICs implement the data-link layer and assign a unique MAC address. Wired NICs use Ethernet standards (IEEE 802.3) with frames delivered to a switch; wireless NICs follow IEEE 802.11 standards. Modern NICs combine a physical interface (PHY) and a MAC; many include features such as speed auto-negotiation, duplex selection, and offload capabilities such as checksum offload, Large Send Offload (LSO), and Large Receive Offload (LRO).

Common forms include wired Ethernet NICs with RJ-45 connectors and wireless NICs that connect to Wi-Fi networks, as well as virtual NICs used by virtualization platforms. In servers and high-performance systems, NIC teaming or bonding combines multiple NICs for redundancy or higher aggregate bandwidth.

Key considerations include supported speeds (from 10 Mbps to 100 Gbps or more), interface type (PCIe, USB, or onboard), driver support, and features such as VLAN tagging (802.1Q) and Wake-on-LAN. Security considerations include MAC spoofing and ARP-related attacks, mitigated by network segmentation and security policies.