Cisco SG300 series switches are capable of detecting CRC errors as can be seen in the interface counters.

But can they correct CRC errors and pass the frame along to the destination or the only way to deal with frames that have CRC errors is to drop them?

This question on StackOverflow explains that single-bit error correction with CRC is possible. Do Cisco switches employ this technique?

I noticed that replacing a non-managed industrial 5-port switch with a Cisco SG300-10 switch fixed sporadic connectivity loss errors between devices on that switch and devices plugged in to another switch.

At the same time the Cisco switch reports non-zero CRC & Align Errors for the uplink interface.

So, can SG300 series switches correct CRC errors?

I studied the Cisco SG300 series switches manual, but did not find an answer.

  • Ethernet has error detection, but not error correction. The switch is simply dropping damaged frames. Apparently, the device you had before would pass the damaged frames on. You seem to have a cabling problem.
    – Ron Maupin
    Commented Feb 12, 2020 at 21:25

1 Answer 1


Do Cisco SG300 switches perform CRC error correction?

No, nor do any other Ethernet switches.[*]

The Ethernet frame's frame check sequence algorithm cannot correct errors, it can only detect them - as long as multiple bit errors don't cancel each other out. Erroneous frames are dropped.

FCS errors do not cause link loss on the physical layer at any time. They usually increase a port counter on managed switches and can cause SNMP traps. If you (also) experience link loss the cable is botched.

Sometimes you can see a difference from one device to another with a cable run that is below spec (too long, below category, kinked, nicked, exceeded pulling force, ...).

Some devices have slightly better margins in their hardware but it can just as well be that a cable that is barely hanging on is very slightly run differently. Double check/replace the patches, recertify the deployed cables and you're stable with any hardware.

[*] You are most likely referring to the data link layer. Some faster physical layer variants use forward error correction - these are able to correct errors at the bit/symbol level.

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