Cisco 4000 Symbol-Err and Sequence-Err

[gilsr]

Hello.

I have Cisco 4000 with supervisor III

Ios version 121-22.E2.

When i check the show interface gigaX/X counter error

I see that on some ports there are Symbol-Err and Sequence Err.

I can't find documentation on theses parameters.

What is the meaning of these parameters? Is there a problem?

In the show int gigaX/X command there are no errors.

Attached a sample output of the command.

[Richard Burts]

Gil

In my experience symbol errors are a problem associated with physical layer problems. The symbol error represents a failure to read data correctly from the media.

Given what you have shown it is difficult to establish whether this is a serious problem or not. I see that the count of symbol errors is 621445 and the number of input packets is 234005239 and that ratio seems pretty high. But I also notice that the interface counters were cleared 2 weeks and 3 days ago. I am not sure whether clearing the interface counters also clears the symbol error count or not. If it does clear then the ratio is high and you probably have a problem that needs attention. If the symbol count is over a longer period of time then it is difficult to know how serious the problem is.

I would suggest that you clear the interface counters again. And then look for the symbol error counter. If it was reset to zero then you probably do have a problem. If the symbol error count was not reset then it is hard to tell the significance of your issue. (but any symbol errors is not a good thing)

HTH

Rick

[gilsr]

Hi.

Clear interface counters clear also Symbol-Err and Sequence-Err.

So what are the meaning of these errors?

[Richard Burts]

Gil

Thanks for confirming that clear counters on the interface also clears the count of symbol errors. It means that the observed ratio of symbol errors to input data is meaningful. And it seems to me that a ratio as high as is observed on your machine indicates that there is a problem in the network.

Symbols have to do with how data in encoded on the fiber. And a symbol error indicates a failure to correctly read data from the fiber. In my experience the symbol errors indicates a problem in the network at layer 1 - usually a probem in cabling.

HTH

Rick