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Network Interface Cards (NICs)

Part of the challenge of passing the Network+ exam is learning about all the different types of hardware a network requires. Today we'll take a look at a vital part of network connectivity, the Network Interface Card (NIC, pronounced "nick").

The NIC is the device, or card, that gives the host a physical connection to the network. The NIC is generally an internal device, but one that can be removed and replaced with a different NIC. NICs are considered Physical layer devices and work at Layer 1 of the OSI model.

Most issues involving NICs occur before the device is even added to the network - because the purchaser didn't do their research. All NICs are not created equal. Some are for Ethernet networks, some for Token Ring, and speed capabilities vary as well. Don't assume a given vendor's NIC is going to fit your device and give you the results you want. A quick visit to the vendor's website and a few minutes looking up NIC specifications can save you a lot of trouble later on.

One more NIC warning - take your time when you're installing a new NIC. Make sure the device is off, and make sure you're properly grounded by connecting the grounding strap to your wrist. Otherwise, you can send static electricity into places on the host where it's only going to cause damage.

Your new NIC should also come with directions on how to download the drivers for that NIC. Drivers sound like something physical, but they're not. Drivers are simply software files that are needed on the host in order for the NIC to work correctly. Vendors used to include drivers on CDs with their NICs, but the trend now is to include instructions on where to download the drivers from the vendor website.

That does lend itself to an occasional Catch-22: "If I don't have this device on the Net yet, how can I download the drivers?" If the host has no network connectivity, you may need to download the drivers to a host that does, copy the files to CD, and then install the drivers from CD.

You'll see two different lights on a typical NIC, one green and one amber. Depending on whether the host has network connectivity or not, the lights will be solid, flashing, or out. Sometimes flashing is good, sometimes it's not! Here's a guide to the colors you'll see on a NIC:

A solid green light indicates connectivity is present. This link light is generally either green or off. Green is good, off is not! That light should stay a solid green. If you see it flashing green, that's a sign of intermittent connectivity, which is a fancy way of saying "one minute the PC is on the network, the next minute it's not". Most likely, either the NIC or the cable connected to the NIC is going bad. With the green light, flashing is not desirable.

Flashing amber lights indicate collisions. You'll see this flash occasionally even on a healthy network, but you don't want to see it flash so often that it looks like a solid amber light!

If you have an Internet connection at home, you can see these lights in action for yourself. The green and amber lights will be right next to where the cable from your modem connects to your PC.

On occasion, you'll have a PC that loses connectivity to the network. I advise you to always start network troubleshooting at the Physical layer of the OSI model, and that means checking both the NIC and the cable connected to it. I personally would swap the cable out first, since they seem to go bad more often than NICs, but that's up to you. If you swap NICs and you still can't get the PC on the network, try putting a new cable in.

About the Author:
Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (, home of free Network + and CCNA tutorials! For my FREE "How To Pass The CCNA" or "CCNP" ebook, visit the website and download your copies. Pass your Network+ exam with The Bryant Advantage!