NIC flash light

what is the NIC card flash light indicate?
i thought the answer is A...
Hiroyuki TamuraField EngineerAsked:
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bentenConnect With a Mentor Commented:
The OSI physical layer relates to electrical signaling. The OSI data link layer relates to LAN level connectivity (as opposed to WAN level). The lights on a NIC typically relate to LAN level connectivity. It is is usually on when the LAN connection is detected and off when one is not detected. It also flashes when link layer data packets are detected on the LAN segment it is attached to. That NIC light is sometimes commonly referred to as a "link light".
JoWickermanConnect With a Mentor Commented:

A NIC operates at both Layer 1 and 2, which is why the TCP/IP model more accurately reflects the functions at those layers than the OSI model does. Yes, a NIC has a MAC address, and performs some Layer 2 functions, but it also is responsible for properly preparing the electrical signals to be transmitted onto the wire (or the RF to be transmitted into the air if you're talking WLAN) and receives and interprets those signals back. Perhaps most sources point to a NIC being a Layer 2 device, in reality, and for purposes of truly understanding networking, a NIC is both a Layer 1 and Layer 2 device.

Hope this clears up some confusion.

aleghartConnect With a Mentor Commented:
The lights are indicators for connectivity, speed, and traffic activity.  You're thinking of a physical failure.

There are no indicators for "I'm physically working."  So, you can't diagnose physical failure by lack of lights.

There may be a firmware problem, switch configuration problem, or NIC configuration problem, which aren't physical in nature.

Good indicators of physical level failure:

--do you smell smoke?
--is that regular or decaf coffee?
--who stole the computer?
Hiroyuki TamuraField EngineerAuthor Commented:
thank you.
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