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N5K to 2960X stack CRC errors

I have 4 stacks switch WS-C2960X connected to N5K-C5672 through VPC.
and from 2960X side use LACP portchannel.

CRC keeps increasing, only on connection to Nexus02, no CRC connection to Nexus01.
I've tried changing SFPs, changing Ports, changing Cables.

 

here my show commands..

 

SW01#sh cdp ne | b Device
Device ID Local Intrfce Holdtme Capability Platform Port ID
Nexus02 Gig 2/0/50 125 R S I C N5K-C5672 Eth 1/29
Nexus01 Gig 1/0/50 159 R S I C N5K-C5672 Eth 1/29

Total cdp entries displayed : 2
SW01#sh int gi 1/0/50 | inc error
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 output errors, 0 collisions, 0 interface resets
SW01#sh int gi 2/0/50 | inc error
66930 input errors, 66450 CRC, 0 frame, 0 overrun, 0 ignored
0 output errors, 0 collisions, 0 interface resets
SW01#
===================
SW02#sh cdp ne | b Device
Device ID Local Intrfce Holdtme Capability Platform Port ID
Nexus02 Gig 1/0/49 122 R S I C N5K-C5672 Eth 1/30
Nexus01 Gig 2/0/49 134 R S I C N5K-C5672 Eth 1/30
SW02#sh int gi 1/0/49 | inc error
43369 input errors, 42988 CRC, 0 frame, 0 overrun, 0 ignored
0 output errors, 0 collisions, 0 interface resets
SW02#sh int gi 2/0/49 | inc error
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 output errors, 0 collisions, 0 interface resets
SW02#
===================
SW03#sh cdp ne | b Device
Device ID Local Intrfce Holdtme Capability Platform Port ID
Nexus02 Gig 1/0/52 177 R S I C N5K-C5672 Eth 1/31
Nexus01 Gig 2/0/52 145 R S I C N5K-C5672 Eth 1/31

Total cdp entries displayed : 2
SW03#sh int gi 1/0/52 | inc error
2758140 input errors, 38073 CRC, 0 frame, 0 overrun, 0 ignored
0 output errors, 0 collisions, 0 interface resets
SW03#sh int gi 2/0/52 | inc error
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 output errors, 0 collisions, 2 interface resets
SW03#

connection looks good, but not sure whats gonna happen in future.

12 REPLIES
Rising star

Re: N5K to 2960X stack CRC errors

Are duplex configured in the same way on both devices?

Duplex mismatch can cause CRC.

 

Regards.

Rising star

Re: N5K to 2960X stack CRC errors

Check also this link:

 

https://community.cisco.com/t5/switching/nexus-5ks-to-2960-x-stack-crc-errors/td-p/2775071

 

CRC could be explained by the switching modality. The cut through mode forwards bad frames transparently from other ports.

So check CRC errors on all ports of the switch.

 

Regards. 

Re: N5K to 2960X stack CRC errors

i checked all ports, CRC appear on port that connected to N5K-02 and interface Port-channel
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 output errors, 0 collisions, 1 interface resets
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 output errors, 0 collisions, 1 interface resets
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 output errors, 0 collisions, 0 interface resets
808 input errors, 800 CRC, 0 frame, 0 overrun, 0 ignored --> Gi 2/0/50
0 output errors, 0 collisions, 0 interface resets
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 output errors, 0 collisions, 1 interface resets
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 output errors, 0 collisions, 1 interface resets
808 input errors, 800 CRC, 0 frame, 0 overrun, 0 ignored --> Po1
0 output errors, 0 collisions, 0 interface resets
SSW#

Re: N5K to 2960X stack CRC errors

Yes.. all port configure at the same duplex
N5K-01# sh int e 1/29 | inc duplex
full-duplex, 1000 Mb/s, media type is 1G
N5K-02# sh int e 1/29 | inc duplex
full-duplex, 1000 Mb/s, media type is 1G
---
SSW#sh int gi 1/0/50 | inc duplex
Full-duplex, 1000Mb/s, link type is auto, media type is 1000BaseSX SFP
SSW#sh int gi 2/0/50 | inc duplex
Full-duplex, 1000Mb/s, link type is auto, media type is 1000BaseSX SFP
Hall of Fame Guru

Re: N5K to 2960X stack CRC errors

Don't put any filters on. We want to see the entire output.
Post the complete output to the command "sh interface <PORTS> CONTROLL".

Re: N5K to 2960X stack CRC errors

here i post both ports connected to N5k01 & N5k02

to_n5k01.pngto_n5k02.png

i found there's different in FCS errors. 

Hall of Fame Guru

Re: N5K to 2960X stack CRC errors

Let me repeat myself: DON'T PUT ANY FILTERS ON.

If it's a "secret" then change the IP address or raise a TAC Case.

Re: N5K to 2960X stack CRC errors

got it.. 

on 2960X stack.. 

sw_1.pngto n5k01sw_2.pngto n5k02

Highlighted
Hall of Fame Guru

Re: N5K to 2960X stack CRC errors

Thanks for this.
The issue is the remote end of Gi 2/0/50.
CRC is "detected" by the receiving end. (You'll never find CRC from the transmission/sender.)
Look at the other side of Gi 2/0/50. If there is no CRC/FCS error then the issue is there. If CRC/FCS is also present (at the "other side") then the issue is the horizontal cabling.
NOTE: You've got other problems other than CRC. The 2960X is dropping packets.

Re: N5K to 2960X stack CRC errors

Many thanks for the explanation Leo.. :) 

 

i've tried to change port. 

SW01 both port-channel member connect to N5K01, after 30mins await no more CRC from SW01.

i believe should be no problem with the SFP and cabling.

 

but this.. SW02 both port-channel member connect to N5K02, both ports get CRC. 

and i checked all switch port connect to N5K02 got CRC.

 

both nexus running same System version: 7.1(0)N1(1b)

sw01.pngsw01sw01b.pngsw01sw02.pngsw02sw02b.pngsw02

 

Hall of Fame Guru

Re: N5K to 2960X stack CRC errors

Here's one way of testing: Swap the fibre between Gi 1/0/50 and Gi 2/0/50.
If the CRC errors go to Gi 1/0/50 then we are sure it's an issue. Since this is fibre, get someone to do an OTDR test of the entire link.
By the way, is the fibre link between the two OM3/OM4?

And how is this path linked together?  Is it:  

2960 stack < --- > patch cord < -- > FOBOT < -- > fibre optic cable < -- > FOBOT < -- > patch cord < -- > Nexus? 

(I want to know how many patch cord/cords and/or how many jumpers, etc.)

Re: N5K to 2960X stack CRC errors

for temporary, i move all portchannel member some stack switch connection to N5K01.
since this is production, and previously use cat4509 was normal, migrate to N5K last week.
the fiber type is OM3, link path is 2960stack <---> Nexus in single patch cord.

anyway, thanks a lot Leo :)
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