[c-nsp] CRC errors on multiple ports of WS-C2950T-48-SI switch

Martin T m4rtntns at gmail.com
Thu Oct 15 05:41:51 EDT 2015


WS-C2950T-48-SI runs only few short startup tests, but those are passed:

POST: System Board Test : Passed
POST: Ethernet Controller Test : Passed
ASIC Initialization Passed



regards,
Martin

On 10/14/15, Steve Mikulasik <Steve.Mikulasik at civeo.com> wrote:
> When it boots up check to see if the switch passes the startup tests.
>
>
> -----Original Message-----
> From: cisco-nsp [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of
> Martin T
> Sent: Wednesday, October 14, 2015 9:15 AM
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] CRC errors on multiple ports of WS-C2950T-48-SI switch
>
> Hi,
>
> I had two WS-C2950T-48-SI switches in the network which all of the sudden
> started to show large amount of CRC errors on about dozen ports. Those two
> incidents are not related to each other, i.e those two incidents did not
> happen at the same time or in the same location.
> I simply received those switches now from remote sites. Unfortunately this
> is all the information I have about the incidents. My first thought was that
> maybe it has to do with the fact that switch has 48 ports and there was
> increased bandwidth between the ports behind different ASICs. I made a
> following physical setup:
>
> Fa0/1 <-> Fa0/48
> Fa0/2 <-> Fa0/47
> Fa0/3 <-> Fa0/46
> ...
> Fa0/24 <-> Fa0/25
>
> Image of the setup can be seen here:
> http://s15.postimg.org/fmsj753qz/WS_C2950_T_48_SI_test_setup.png
>
>
> VLANs were configured like this:
>
> WS-C2950T-48-SI#sh int status
>
> Port      Name               Status       Vlan       Duplex  Speed Type
> Fa0/1                        connected    1          a-full  a-100
> 10/100BaseTX
> Fa0/2                        connected    2          a-full  a-100
> 10/100BaseTX
> Fa0/3                        connected    3          a-full  a-100
> 10/100BaseTX
> Fa0/4                        connected    4          a-full  a-100
> 10/100BaseTX
> Fa0/5                        connected    5          a-full  a-100
> 10/100BaseTX
> Fa0/6                        connected    6          a-full  a-100
> 10/100BaseTX
> Fa0/7                        connected    7          a-full  a-100
> 10/100BaseTX
> Fa0/8                        connected    8          a-full  a-100
> 10/100BaseTX
> Fa0/9                        connected    9          a-full  a-100
> 10/100BaseTX
> Fa0/10                       connected    10         a-full  a-100
> 10/100BaseTX
> Fa0/11                       connected    11         a-full  a-100
> 10/100BaseTX
> Fa0/12                       connected    12         a-full  a-100
> 10/100BaseTX
> Fa0/13                       connected    13         a-full  a-100
> 10/100BaseTX
> Fa0/14                       connected    14         a-full  a-100
> 10/100BaseTX
> Fa0/15                       connected    15         a-full  a-100
> 10/100BaseTX
> Fa0/16                       connected    16         a-full  a-100
> 10/100BaseTX
> Fa0/17                       connected    17         a-full  a-100
> 10/100BaseTX
> Fa0/18                       connected    18         a-full  a-100
> 10/100BaseTX
> Fa0/19                       connected    19         a-full  a-100
> 10/100BaseTX
> Fa0/20                       connected    20         a-full  a-100
> 10/100BaseTX
> Fa0/21                       connected    21         a-full  a-100
> 10/100BaseTX
> Fa0/22                       connected    22         a-full  a-100
> 10/100BaseTX
> Fa0/23                       connected    23         a-full  a-100
> 10/100BaseTX
> Fa0/24                       connected    24         a-full  a-100
> 10/100BaseTX
> Fa0/25                       connected    25         a-full  a-100
> 10/100BaseTX
> Fa0/26                       connected    24         a-full  a-100
> 10/100BaseTX
> Fa0/27                       connected    23         a-full  a-100
> 10/100BaseTX
> Fa0/28                       connected    22         a-full  a-100
> 10/100BaseTX
> Fa0/29                       connected    21         a-full  a-100
> 10/100BaseTX
> Fa0/30                       connected    20         a-full  a-100
> 10/100BaseTX
> Fa0/31                       connected    19         a-full  a-100
> 10/100BaseTX
> Fa0/32                       connected    18         a-full  a-100
> 10/100BaseTX
> Fa0/33                       connected    17         a-full  a-100
> 10/100BaseTX
> Fa0/34                       connected    16         a-full  a-100
> 10/100BaseTX
> Fa0/35                       connected    15         a-full  a-100
> 10/100BaseTX
> Fa0/36                       connected    14         a-full  a-100
> 10/100BaseTX
> Fa0/37                       connected    13         a-full  a-100
> 10/100BaseTX
> Fa0/38                       connected    12         a-full  a-100
> 10/100BaseTX
> Fa0/39                       connected    11         a-full  a-100
> 10/100BaseTX
> Fa0/40                       connected    10         a-full  a-100
> 10/100BaseTX
> Fa0/41                       connected    9          a-full  a-100
> 10/100BaseTX
> Fa0/42                       connected    8          a-full  a-100
> 10/100BaseTX
> Fa0/43                       connected    7          a-full  a-100
> 10/100BaseTX
> Fa0/44                       connected    6          a-full  a-100
> 10/100BaseTX
> Fa0/45                       connected    5          a-full  a-100
> 10/100BaseTX
> Fa0/46                       connected    4          a-full  a-100
> 10/100BaseTX
> Fa0/47                       connected    3          a-full  a-100
> 10/100BaseTX
> Fa0/48                       connected    2          a-full  a-100
> 10/100BaseTX
> Gi0/1                        connected    1          a-full a-1000
> 10/100/1000BaseTX
> Gi0/2                        connected    25         a-full a-1000
> 10/100/1000BaseTX
> WS-C2950T-48-SI#
>
>
> While I don't know the internal architecture of WS-C2950T-48-SI switch and
> it has no "sh platform" command which might reveal anything, then at least
> based on traces on the PCB first half of the ports seem to be connected to
> first Broadcom BCM5649B0KPB ASIC and second half of the ports seem to be
> connected to second Broadcom BCM5649B0KPB ASIC. Now if I send 100Mbps of
> traffic through all the switch ports, then there are frame drops because of
> ingress buffer overflow, but no CRC errors.
> In addition, if I decrease bandwidth to 70Mbps, then there are no more
> ingress buffer drops. Last but not least, those two switches served fairly
> low-speed connections and most of the traffic was between FastEthernet and
> GigE uplink-ports.
>
> What might cause vast amount of transient CRC errors on multiple switch
> ports? Maybe the PCB of WS-C2950T-48-SI switch is known to be especially
> receptive to EMI? Any other ideas?
>
>
>
> thanks,
> Martin
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