Validation of FCS

Jason Lixfeld jason at
Wed Dec 19 14:53:26 UTC 2012

Hi all, 

I'm trying to confirm (or debunk) my current understanding of FCS errors.  An FCS error is a layer 2 error.  In Ethernet spake, the 4 bytes of FCS data within each Ethernet frame is validated by a CRC check, which is done by the device receiving said frame.  If the CRC check fails, an FCS error is reported by that receiving device.

If that understanding is true and presuming a "circuit" was made up of many layer 2 devices between the A and Z side of said circuit, it would be impossible for a CRC error somewhere along the path of that circuit to register on the receiving device of either the A or Z side.  Perhaps in simpler terms, a CRC error is a localized thing and would never be forwarded from one device to another.

Is that fair and/or accurate?

Thanks in advance.

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