[c-nsp] CRC errors on multiple ports of WS-C2950T-48-SI switch
Steve Mikulasik
Steve.Mikulasik at civeo.com
Wed Oct 14 12:12:18 EDT 2015
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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