Definition of "show hardware internal carmel crc"

[PeterJacobsen]

Hi Guys

Does anyone know the definition/output of NX-OS command “show hardware internal carmel crc”?

The output is eight column table, like below. I can’t find explanation of the column names like MM tx CRC etc.
I know about Tx Rx and CRC, but not the FI and MM.

+----------+------------+------------+------------+------------+------------+------------+------------+
|   Port   | MM rx CRC  | MM Rx Stomp| FI rx CRC  | FI Rx Stomp| FI tx CRC  | FI tx Stomp| MM tx CRC  |
+----------+------------+------------+------------+------------+------------+------------+------------+
| Eth 1/1  |        --- |        --- |        --- |        --- |        --- |       1740 |       1740 |
| Eth 1/2  |        --- |          2 |        --- |          2 |        --- |        168 |        168 |
| Eth 1/3  |        --- |        --- |        --- |        --- |        --- |          2 |          2 |
| Eth 1/4  |        --- |        --- |        --- |        --- |        --- |         20 |         20 |
| Eth 1/5  |        --- |        --- |        --- |        --- |        --- |        --- |        --- |
| Eth 1/6  |        --- |        --- |        --- |        --- |        --- |        --- |        --- |
| Eth 1/7  |        --- |        --- |        --- |        --- |        --- |        --- |        --- |
| Eth 1/8  |        --- |        --- |        --- |        --- |        --- |       1439 |       1439 |
| Eth 1/9  |        --- |        --- |        --- |        --- |        --- |        --- |        --- |
| Eth 1/10 |     472005 |        --- |        --- |     467858 |        --- |        164 |        164 |

I’m troubleshooting interface errors on Nexus 5000, probably caused by MTU violation.

TIA

Peter

[Furose M]

A CRC error is for a store-and-forward switch. When they get a corrupted packet, they recalculate the CRC value, and if the CRC value doesn't match what they see, the packet is dropped and the CRC error is incremented.

In a cut-through switch, we start to forward the packet as we receive it without even being able to look at the whole packet. If we have packet corruption, and the CRC value doesn't match, we can't drop the packet, since we've already started to forward it. So we put a special "stomp" value in the CRC field. We will increment our Tx Stomp counter, and the next switch that receives the "stomped" packet will increment its Rx Stomp counter.

[PeterJacobsen]

Thanks Furose

But what is the difference between MM Tx Stomp and FI Tx Stomp?

[Furose M · Accepted solution]

MM means "Multimedia MAC" and refers to frames off the wire before they hit other internal components of the switch. The "FI" means "Forwarding Interface" and refers to the frame after it has been processed by the ASIC.

whenever the MM counter increases, you will also see FI counter increment. its not necessary vice versa.

if both counter increments, that means, the packets that the switch received was having stomp.. if only FI increases, its being stomped internally, so something wrong on the switch.

[PeterJacobsen]

Thank you very much Furose for your time and explanation. :-)

Peter