Exam N10-008 topic 1 question 7 discussion

The data unit on Layer 2 is a frame. Each frame contains a frame header, body, and a frame trailer: Header: typically includes MAC addresses for the source and destination nodes. Body: consists of the bits being transmitted. Trailer: includes error detection information. When errors are detected, and depending on the implementation or configuration of a network or protocol, frames may be discarded or the error may be reported up to higher layers for further error correction. Examples of error detection mechanisms: Cyclic Redundancy Check (CRC) and Frame Check Sequence (FCS). Learn more about error detection techniques here. Answer is Layer 2 (B)

I had this on my exam, and I answered A. Now, I believe that's incorrect in light of my score report, which included this objective: "1.1 Compare and contrast the Open Systems Interconnection (OSI) model layers and encapsulation concepts." I'm all but 100% certain it's because I misanswered this, which is the only OSI-related question I can remember. B is most likely the correct answer. CompTIA's rationale? I'll try to guess. First step in the troubleshooting methodology is to identify the problem. You would probably have to start at Layer 2 for the "identify symptoms" substep, where you'd check the CRC errors themselves on a data-link interface You wouldn't go to Layer 1 until step 2, when you "establish a theory of probable cause." Most likely the technician would theorize physical (cabling) issues and test it accordingly, but that's not during the FIRST troubleshooting step.

Its actually Layer 1 because CRC occurs in Layer 2 because of Physical layers (Layer 1) problems: Such as "Network Cables, Connectors, Ports as well interference" all these can cause CRC errors which can be seen at layer 2.

The administrator would most likely start troubleshooting at Layer 2 (Data Link layer) of the OSI model. CRC (Cyclic Redundancy Check) errors are often associated with the Data Link layer, where frames are checked for errors. CRC errors usually indicate issues with the data integrity at this layer, which could be due to network device configuration problems, faulty cables, or interference affecting the physical transmission.

CRC (Cyclic Redundancy Check) errors typically occur at the Data Link layer (Layer 2) of the OSI model. This layer handles error detection and correction for node-to-node data transfer, so it’s the most logical place to start troubleshooting for such issues.

CRC errors are related to Layer 1(physical layer) due to cable faults improper crimping , damages or other signal issues, should be Layer 1 as answer.

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

7. Application Layer 6. Presentation Layer 5. Session Layer 4. Transport Layer 3. Network Layer 2. Datalink Layer (Sender and receiver info mismatch) 1. Physical Layer

From the Official CompTIA Network+ Study Guide: "TROUBLESHOOTING INTERFACE ERRORS As well as monitoring for traffic bottlenecks and other performance issues, interface errors might indicate a misconfiguration problem at the data link layer or interference at the physical layer. Cyclic Redundancy Check Errors A cyclic redundancy check CRC is calculated by an interface when it sends a frame. A CRC value is calculated from the frame contents to derive a 32-bit value."

Changed my mind to A. Administrator would START troubleshooting at Layer 1 first.

The CRC errors typically indicate issues at the physical layer (Layer 1) of the OSI model, so the administrator would likely start troubleshooting there. Therefore, the correct answer is A. Layer 1.

In summary, while CRC is useful for local error detection within a single hop (e.g., within a LAN segment), it doesn’t cover end-to-end communication. Each layer’s specific checks serve different purposes, ensuring robustness and reliability throughout the network. Therefore, starting troubleshooting at Layer 1 is the most logical approach

CRC errors typically occur at Layer 1 of the OSI model, which is the physical layer responsible for transmitting raw binary data over the network medium. CRC errors indicate issues such as faulty cabling, loose connections, electromagnetic interference, or problems with network interface cards (NICs). Therefore, the administrator would begin troubleshooting at Layer 1 to address these physical layer issues.

CRC IS L2

Ethernet frame CRC (FCS) is usually understood to be on OSI layer 2

Cyclic Redundancy Check is a powerful algorithm that is used for error control in the data link layer. The number of 0 bits appended on the sender's side is equal to the highest number of polynomial degrees.

CRC (Cyclic Redundancy Check): It's an error-detection mechanism used at Layer 2 (Data Link Layer) to ensure data integrity during transmission. Layer 1 Involvement: However, CRC errors often indicate underlying physical layer issues, such as: Faulty cables Loose connections Interference Hardware defects