Exam N10-008 topic 1 question 585 discussion

CRC errors mean that packets have been damaged. This can be caused by a faulty port on the device or a bad Ethernet cable. Changing the cable or swapping the port is a relatively easy fix. Occasionally, they are generated on layer 2 by a duplex mismatch. It can also be the result of collisions or a station transmitting bad data. source: Exam Topics N10-008 Study Guide I am going with bad port because of the reference to ethernet cable as opposed to fiber...

A. Break in the fiber Please reference link to Cisco page below. " Root Causes of CRC Errors The most common root cause of CRC errors is a damaged or malfunctioning component of a physical link between two devices. Examples include: vvvv 1. Failing or damaged physical medium (copper or fiber) or Direct Attach Cables (DACs). 2. Failing or damaged transceivers/optics. 3. Failing or damaged patch panel ports. 4. Faulty network device hardware (including specific ports, line card Application-Specific Integrated Circuits [ASICs], Media Access Controls [MACs], fabric modules, etc.), 5. Malfunctioning network interface card inserted in a host. " https://www.cisco.com/c/en/us/support/docs/ios-nx-os-software/nx-os-software/217554-understand-cyclic-redundancy-check-crc.html

I agree that CRC almost always means cable issue, but this is fiber. A break in the fiber would almost certainly halt all communications, not cause CRC errors. It's not D. So I'm torn between B and C. Both are acceptable answers but I think this comes down to emphasizing the MOST likely cause. My guess would be the switch port went bad, but I'll consider this question a wash if I get it on the exam.

Cables = CRC

it's hard to chose on this one because both A and C answer can cause CRC errors.

A. Break in the fiber CRC (Cyclic Redundancy Check) errors on a SAN (Storage Area Network) switch are often associated with issues in the physical layer, such as breaks or issues in the fiber optic cables. A break in the fiber can lead to signal degradation and result in CRC errors. Therefore, the MOST likely cause of CRC errors in this scenario is A. Break in the fiber.

This case it should be C

A. Break in the fiber CRC (Cyclic Redundancy Check) errors in a Storage Area Network (SAN) switch are often indicative of physical layer issues, such as a break in the fiber optic cable. CRC errors occur when there is a mismatch or corruption in the data during transmission. In the context of a SAN switch, issues with the fiber optic cable, connectors, or transceivers can lead to CRC errors. While other issues like a bad switch port or mismatched duplex could potentially cause network errors, CRC errors specifically point to problems with the integrity of the data being transmitted, which is commonly associated with physical layer issues like a break in the fiber. Therefore, the most likely cause of the CRC errors in this scenario is A. Break in the fiber.

CRC errors and/or late collisions can be caused by a duplex mismatch. When one site of a link is configured on full-duplex and the other on half-duplex you will see the CRC errors at the interface which is configured on full-duplex. This problem occurs also when one site of a link is configured on auto-duplex and the other fixed (full-duplex).