CRC Errors = Faulty Cable = Physical = Layer 1

The question stated "Administrator MOST likely start to troubleshoot when a network is experiencing a number of CRC errors?, therefore, the answer will be letter A. Start from Bottom to Top.

B. Layer 2 CRC (Cyclic Redundancy Check) errors typically occur at the data link layer, which corresponds to Layer 2 of the OSI model. Therefore, when troubleshooting a network experiencing CRC errors, the administrator would MOST likely start at: Layer 2 includes protocols such as Ethernet that deal with the framing and addressing of data on the local network segment. CRC errors often indicate issues with the integrity of the data as it is transmitted across the network at this layer.

I would say Layer 2, mainly because CRC errors are inherent to the Data Link Layer. While it's true that faulty cables could be the reason (so you would act on the Physical L1), I think the keyword here in the question is "START to troubleshoot [..]", meaning you wouldn't immediately begin to replace all cables in the LAN right off the bat. Answering A is overthinking it.

CRC errors occur from misconfigured, or simply malfunctioning cables on layer 1. CRC-4 checks for data transmission errors on E1 trunk lines at the data link layer (Layer 2) or transport layer (Layer 4) of the OSI model for how applications communicate over a network. An error is said to have occurred when there is a mismatch between the receiver's information and the sender's information, thus involving the frames. Question 7 said this was layer 2 so that's weird, lol.

it doesnt make sence to start at 2 be we dont know what is the problem but we do know the possoble cause, and when trobloshooting you start with the simple obvios fix before excleating

"Data Link Layer (Layer 2): The Data Link Layer is responsible for the reliable transmission of data between adjacent network nodes. Error detection and correction techniques, such as the use of checksums or cyclic redundancy checks (CRC), are commonly implemented at this layer"

Messor says B however, this question on the test actually doesn't have layer 2 as an option

i say layer 2 question the obvious or as professor messer says "start with the obvious" crc= bad layer 2 hardware https://www.youtube.com/watch?v=L-hlrK9Dq7I

B Layer2

More or less the same as earlier question 7. "A network is experiencing a number of CRC errors during normal network communication. At which of the following layers of the OSI model will the administrator MOST likely start to troubleshoot?" Correct answer B - layer 2

OSI layer 2 data units are called frames and Layer 3 data units are called packets, Layer 4 are segments. CRC refers to frames and thus to Layer2 Errors.

In question 7 there os normal network communication in progress going on, you would only be able to troubleshoot layer 2 without causing interference. If there is not normal network communications going on like in this question, you can check the layer 1 cables, ports & transceivers.

In question 7 there is normal network communication in progress going on, you would only be able to troubleshoot layer 2 without causing interference. If there is not normal network communications going on like in this question, you can check the layer 1 cables, ports & transceivers.

CRC errors are usually caused by interference. This interference might be due to poor quality cable or termination, attenuation, mismatches between optical transceivers or cable types, or due to some external factor These issues are on Layer 1

Layer 2 is the Answer to this question. Researched On all other platforms

When a network is experiencing a large number of cyclic redundancy check (CRC) errors, which occur when data is corrupted during transmission, the administrator should start troubleshooting at the Physical Layer, which is the first layer of the OSI model.