Cisco Certified Network Associate (CCNA) Practice Exam

What type of errors may indicate problems with the physical network layer?

1. Soft errors

2. CRC errors

3. Packet drops

4. Routing errors

The correct answer is: CRC errors

CRC (Cyclic Redundancy Check) errors are a specific type of error that can indeed indicate issues at the physical network layer. When data is transmitted over a network, it is often accompanied by a CRC value that allows the recipient to verify the integrity of the received data. If the CRC value does not match the calculated value from the received data, this discrepancy typically points to corruption that has occurred during the transmission. Such corruption can result from various physical issues, such as interference, signal degradation, or problems with cabling or connectors. In contrast, soft errors are usually transient issues not necessarily linked to physical components but more to the data being processed. Packet drops can occur at any layer due to congestion or buffer limitations, rather than directly indicating physical layer problems. Routing errors relate to issues in the network layer itself, such as incorrect routing tables or misconfigurations, rather than issues in the physical layer of the network. Therefore, CRC errors are the best indicator of potential problems specifically related to the physical network layer.