Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 
Community Member

System FCS error frames on Catalyst 3750


may someone explain what are the "System FCS error frames" I see with "show controllers ethernet-controller" on some ports of a Catalyst (on trunk and also on access ports) WS-C3750G-24TS-S (3 switches in stackwyse)?

Error counters advance slowly, but they do grow... and I am afraid this could be the reason for variable slow access time to a server application menu...

For example "8 System FCS error frames".

The ports are connected to a PIX-515E and I see the same error count on the firewall interfaces (PIX "show interface" command shows me "8 input errors, 8 CRC, 0 frame, 0 overrun, 8 ignored, 0 abort")

A few errors may be seen also on other ports, connected to other (C3550)switches.

I tried to upgrade the IOS version, so I loaded "ipbase 12.2(25)SEB4 " on the Catalyst 3750, but it did not solve the problem.

PIX firewalls are running software 6.3(4).

Why these errors are called "System FCS error frames" ? I could not find anything searching on Cisco CCO!


Cisco Employee

Re: System FCS error frames on Catalyst 3750

The "System FCS error frames" counter indicates the total number of frames that fail FCS check when they are received by the egress ASIC from the internal or external StackWise ring. This indicates the frames are corrupted inside the 3750 stack. Under normal circumstances, you should never see any System FCS error frames unless there is a problem with the StackWise cable. Make sure the stackwise cables are seated properly and screws tightened.

Community Member

Re: System FCS error frames on Catalyst 3750

I apologies for the delay answering, my notebook has been down for 5 days and also cco access password...

Thank you for the explanation and suggestion.

We have a second rack with another three switch 4750 in stackwyse, same models as the "faulty" ones, and the errors are not present on those switches, so it must be something hardware related on the first group of switches.

I cannot touch those devices at the moment, we captured traffic frames with 3 Notebook PCs running "Ethereral" lan sniffer, traffic to and from the server and two clients and we discovered that in different ports of those switches, some packets never reach the clients, causing many TCP retransmissions, especially witch continuous traffic (http get and ftp transfers). This problem is visible on some, but not all, of the catalsyt 3750 switches in stackwyse, but in every one of the three switches. We are planning to go on-site and replace the hopefully faulty one ( or reseat the cables as you suggested).

Is this a problem you have seen before?


Franco Feri

CreatePlease to create content