Network Interface Cards (NICs)

How does your computer or mobile device connect to the network in your home or your company’s internal network? How are your devices able to transmit, receive, and process information from the Internet? The magic lies in a small card called a Network Interface Card (NIC) built-in to your device. You might also hear them referred to as a network card, network adapter, or LAN adapter…they’re all the same thing.

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NICs are both layer 1 (Physical) and layer 2 (Data Link) devices. They occupy both layers because they physically put frames out onto the wire or radio frequencies, and they talk to the OS through a device driver in order to (de)encapsulate IP packets with Ethernet or 802.11 headers. However, CompTIA thinks of NICs more as layer 2 devices.

NICs interact with a “device driver,” which is a program that controls how the NIC communicates with your device’s operating system. The operating system doesn’t directly communicate with the NIC, but the device driver is the software that controls the NIC.

Types of NICs

NICs usually come in four different types, discussed below.

UTP Ethernet NICs

The first kind of NIC is a UTP NIC. “UTP” stands for “Unshielded Twisted Pair” cabling. UTP cabling is the predominant form of cabling used on our wired networks and it comes in many different categories, but that is beyond the scope of this post. However, feel free to study the diagram below of the different categories of UTP cables.

CAT ratings

UTP cabling is heavily relied on for our wired, Ethernet networks. Some extremely common type of UTP cables are CAT5e, CAT6, and CAT6a. The “CAT” stands for the “category” of the cable. The higher the CAT number, the better the frequency and bandwidth for that cable.

The most common type of connector attached to UTP cables are RJ-45 connectors. You’ve probably seen them yourself since they’re so popular. RJ-45 connectors are an 8-position-8-conductor connector. The standard UTP cables used these days contain 4-pairs of wires inside them, which equals 8 wires in total. Look closely at the RJ-45 connector below and count the number of pins. It should total 8 pins.

rj-45 2.jpg

Most NICs that are connected to a wired LAN are connected to a switch via a UTP stranded core patch cable, just like the one below. The RJ-45 connector neatly fits inside the RJ-45 port on the NIC, allowing the computer to connect to the network.


Fiber-Optic NICS

Fiber-Optic NICs are like UTP NICs, but they come in a wide variety of connector types or ports. Fiber-Optics cabling manufactures use many, many different types of fiber-optic connectors, such as SC connectors, LC connectors, and MT-RJ connectors. Therefore, fiber-optic NICs are not easy to identify unless you know the connector type.

Fiber-optic cables don’t use electricity to transmit data across the wire, like UTP cables. Instead, fiber-optic cables transit data using light pulses. These light pulses are generated either via LEDs or lasers. If you’re using lasers, your data can travel between 2km and 10km, based on the IEEE 802.3 standard you are using!

Here’s a small slide show of different fiber-optic NICs and their different fiber-optic connectors.

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Wireless NICs

NICs can also be wireless and they are mainly used in our mobile devices, like laptops. Wireless NIC operate with the same concept as wired, UTP NICs. However, wireless NICs are manufactured to use the IEEE 802.11a/b/g/n/ae (wireless) standards. Wireless NICs use an antenna to transmit information onto the network via different radio frequencies. These wireless NICs can have the antenna built into the NIC or displayed outside of the NIC, just like the example below.


Installing NICs

This section won’t be very long because, fortunately, installing NICs are very, very easy. Since most computers have built-in NICs, you may not ever have to install a NIC unless your built-in NIC breaks or you want to add an additional, updated NIC for your network. Most motherboards have two types of expansion slots

Peripheral Component Interface (PCI) Slots

The PCI slot was created in 1994. Most motherboards have them on there anyway in 32-bit and 64-bit bus width. “Throughput” varies by bus version: 133 MB/s (32-bit at 33MHz to 533 MB/s  and 64-bit at 66 MHz). Throughput is the amount of material or items passing through a system or process. All you have to do is insert the NIC into the PCI slot and your done!

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PCI express (PCIe) slots

On newer motherboards these days, you are going to find PCI express (PCIe) slots. It’s not really a bus in a traditional sense. It has unidirectional serial lanes, X1, x2, x4, x8, x16, x21 full-duplex lanes (“x” is pronounced as “by,” for example, “by 4” or “by 16”). I’ve included both PCI and PCIe slots in the image below to show the differences.

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NIC Link Lights

Most UTP Ethernet NICs have “link lights,” or little LEDs that light up to indicate connection status, network activity status, or collision status (this light is not usually seen on modern Ethernet NICs). As a network tech, you’ll have to know what each one of these lights mean. If your connection light is flickering or is not lit up, it’s an indication of a problem. If there is a problem with the connection light, make sure nothing is disconnected. If there is not a cable disconnection issue or a damaged cable, you can pull up the device management utility by typing devmgmt in the Windows command prompt to check the status of the NIC or if there needs to be a driver update. If your NIC comes with diagnostic software, you may also run it and perform a loopback test, if possible.

link lights.jpg

Fiber-optic NICs don’t come with link lights, thus, diagnosing problems with fiber-optic NICs can sometimes be challenging. If that’s not challenging enough, there exits no standard that governs how manufacturers use their link lights. This means that different NICs are going to have different colored link lights and layouts. But, no worries. If you buy a name-brand NIC, the troubleshooting instructions can be found in the documentation and they’re much easier to troubleshoot.


Meyers, M. (2015). All in One CompTIA Network+ Certification Exam N10-006. McGraw-Hill Education: New York, NY.

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