Network interface card (NIC)
A network card (network adapter, NIC) is a device that connects a computer or server to a network and exchanges data in the form of frames. It converts computer data into signals for transmission over cable or Wi-Fi and has a unique MAC address.
A network card (network adapter, NIC) is a device that connects a computer or server to a network and exchanges data in the form of frames. It converts computer data into signals for transmission over cable or Wi-Fi and has a unique MAC address by which the network locates it.
What is a network card
A network card (NIC, Network Interface Card) is a computer component that connects it to an Ethernet, Wi-Fi or fiber optic network. The main function of a network card is to receive and transmit data: it takes digital application data, forms network frames from it, adding the sender's and recipient's MAC addresses, and sends them into the transmission medium (cable or radio channel). On the way back, the card receives frames, recognizes its own and passes them to the operating system. Modern network cards can be built into the motherboard (usually 1–2.5 Gbps), installed in a PCIe slot (from 1 to 100 Gbps) or connected via USB. For servers, cards with support for port aggregation, VLAN and protocol offload, which reduces the load on the processor, are used.
Types and speeds
By data transfer rate, adapters are divided into classes: Fast Ethernet — 100 Mbps (obsolete); Gigabit Ethernet — 1 Gbps, the standard for workstations; 2.5 and 5 GbE — accelerated for new PCs and servers; 10/25/40/100 GbE — for data center servers, storage systems and the network core. By interface type: PCIe adapters (internal), USB adapters (for laptops and small systems) and built-in motherboard adapters. By transmission medium: copper (twisted pair RJ-45), optical (SFP/SFP+ modules) and wireless (Wi-Fi/Wi-Fi 6E). The network card operates at the data link layer and interacts with the switch: the latter uses the MAC address to direct frames from one adapter to another.
Setting up and diagnosing a network card
For stable operation, up-to-date drivers are installed and the speed and duplex are checked to be automatically matched with the switch port. With low performance, the link status and error counters in the adapter properties are checked, the firmware is updated and, if necessary, power saving (Green Ethernet) that slows down transmission is disabled. For servers, port aggregation (LACP/teaming) and protocol offload, which reduce the load on the processor, are configured, and diagnostics are performed using OS tools and traffic analyzers. A card failure manifests itself in loss of communication, delays or errors at the data link layer, so fallback ports are used for critical servers, and a spare adapter is kept in reserve for quick replacement without stopping work.
When choosing a network card for a workstation, they focus on the port speed (1 Gbps is enough for most tasks) and the connection interface (PCIe or USB). For servers, models with two or more ports, support for protocol offload and virtualization functions (SR-IOV) are chosen, which increases performance when working with many virtual machines. The cost of an adapter grows with the declared speed and feature set, so for ordinary stations it is not reasonable to overpay for multi-port industrial models.
Frequently asked questions
What is a network card?
A network card (NIC) is a device for connecting a computer to a network. It forms network frames, labels them with its MAC address, transmits them over cable or Wi-Fi and receives data addressed to this computer.
How is a 1 Gbps NIC different from a 10 Gbps one?
In data transfer speed: 1 Gbps is a classic for workstations and small servers; 10 Gbps and higher is for data center servers, storage systems and the network core, where high-load bandwidth is required.
How to find out the MAC address of a network card?
A MAC address is a unique six-byte address defined by the manufacturer (the first three bytes) and the device serial number. In Windows it is viewed with the ipconfig /all command, in Linux — with ip link, on servers — on the label or in the OS interface.
Why does a server need several network cards?
Several ports allow aggregating channels (increasing bandwidth and reliability), separating traffic (management/data/backup) and connecting the server to several networks at once. The cards support VLAN and protocol offload.
What is offload on a network card?
Offload is the transfer of part of the processing of network protocols (checksums, packet segmentation) to the card hardware instead of the processor. This reduces the CPU load and speeds up processing of large data flows on servers.
Which adapter should I choose for a laptop?
For a laptop, a built-in Wi-Fi 6/6E is usually enough; for stable operation over cable, a USB Gigabit Ethernet adapter is used. For professional tasks, a USB-C adapter with 2.5–10 Gbps support is suitable.
What is an SFP module on a network card?
SFP/SFP+ is a removable optical module installed in a slot on a network card or switch for connecting fiber optics. It determines the speed (1–25 Gbps) and the type of line (single-mode or multimode fiber).
Which OSI layer does a network card operate at?
A network card operates at the second (data link) layer of the OSI model: it forms and transmits frames with MAC addresses in the transmission medium. Routing between networks is performed higher, at the network layer, by routing devices.
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Network interface card (NIC)
A network card (network adapter, NIC) is a device that connects a computer or server to a network and exchanges data in the form of frames. It converts computer data into signals for transmission over cable or Wi-Fi and has a unique MAC address.
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