Troubleshooting CRC Errors
Overview
This document explains how to troubleshoot cyclic redundancy check (CRC) errors that occur in your network infrastructure. Follow the guidance in this document to identify the root causes of CRC errors and implement solutions that restore optimal data transmission performance. CRC checks are crucial for ensuring data integrity in networks. These checks detect errors, and in some cases correct them, before the errors cause significant communication problems.
Troubleshooting CRC errors
Network devices use CRC to detect errors in transmitted data.
The sending device generates a value derived from the remainder of a polynomial division of its data contents. The receiving device compares the recalculated CRC value with the value received along with the data. If the two CRC values match, the data was not corrupted during transmission.
A mismatch between the received CRC value and the recalculated CRC value causes the receiving device to flag a CRC error. When the Cisco Meraki MS switch reports CRC errors on the Meraki dashboard, the data was likely altered or corrupted during transmission.
Troubleshooting steps
Follow these steps to troubleshoot CRC errors:.
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- Confirm that the CRC errors are incrementing. If the errors are incrementing, move the cable to a different switch port, then go to step 2.
- Determine whether the CRC errors move to the new switch port (using the same cabling and end device).
- If the CRC errors are no longer present, the original switch port could be the issue. Connect a different device and Ethernet cable to the original port. If the CRC errors continue to increment, the switch port is most likely the issue. End the troubleshooting process here.
- If the CRC errors move to the new switch port, the cabling could be the issue.
- If a patch panel connects the switch and the end device, bypass the patch panel and connect the end device directly to the switch, then go to step 3.
- If there is no patch panel, change the cable to see if the CRC errors disappear, then go to step 4.
- Determine whether the CRC errors continue to increment after you bypass the patch panel.
- If the CRC errors stop, the patch panel cable could be the issue. End the troubleshooting process here.
- If the CRC errors continue, change the cable to see if the CRC errors disappear, then go to step 4.
- Determine whether the CRC errors still increment after you change the cable.
- If the CRC errors stop, faulty cabling caused the CRC errors. End the troubleshooting process here.
- If the CRC errors continue, check whether the speed and duplex settings match on the switch and the end device, then go to step 5.
- Determine whether the speed and duplex settings match.
- If the settings do not match, change the speed and duplex settings so that they match. If the CRC errors stop, the client device is the issue.
- If the settings match, replace the end device. If the CRC errors stop, the client device is the issue. End the troubleshooting process here.