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CRC Errors

Hi all I have a Cisco 3750 connected via a SMOF SFP Port to a Cisco 2940 (Gi0/1) SFP port Only on the 3750 am I seeing CRC errors, not a huge amount, less than

1% but CRC errors all the same. I tried replacing the cable and the SFP on the 3750 switch with the same result. What I ended up doing to eliminate the SFP port on the 3750 was this Plug the SMOF fibre from the 3750 into another 2940 SFP and connecting this newly installed 2940 back into the 3750 via an Ethernet cable

Original config

3750 Gi1/0/28 ---> 2940 Gi0/1 using SMOF

New config

3750 Gi1/0/11 Ethernet ----> 2940 Fa0/1, 2940 Gi0/1 SFP ------> 2940 Gi0/1 SFP

Only on the 3750 am I seeing CRC errors, it can't be the fibre cable I believe as this is now a UTP ethernet cable eliminating the fibre, I am not seeing any errors on any other ports just Gi1/0/11 on the 3750

Here is the port config on the 3750 interface GigabitEthernet1/0/11 switchport trunk encapsulation dot1q switchport trunk allowed vlan 8,141 switchport mode trunk no ip address duplex full speed 100 no mdix auto spanning-tree portfast end

And here is the 2940 port config interface FastEthernet0/1 switchport trunk allowed vlan 8,141 switchport mode trunk speed 100 duplex full spanning-tree bpdufilter enable end

I have set the duplex and speed manually on both ends as I have seen this cause CRC and Input errors in the past, but it has made no difference.

Any advice would be most appreciated. Any questions with regards to this please shoot and I will endevour to answer them

Regards Scott

Reply to
Scooty
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Go back to the original setup you intended.

3750 Gi1/0/28 ---> 2940 Gi0/1 via fibre.

  1. Is there another free fibre port on the Cisco3750? Move the fibre+SFP to the available port. This will eliminate if Gi1/0/28 is faulty itself.

If still seeing CRC

  1. Replace the SFP GBIC plugged into Gi1/0/28. This will eliminate if the SFP GBIC is bad.

If still seeing CRC

  1. Replace the fibre. This will eliminate the fibre.

If still seeing CRC

  1. Repeat 1-3 for the Cisco2940.

A good rule of thumb in troubleshooting is "Divide and conquer".

Scooty wrote:

Reply to
brickwalls19

Good troubleshooting technique described above.

I just wanted to mention to the OP that your idea of reasonable error rates with fibre ethernet is not quite the same as mine.

This is a reasonable error rate.

88231052239 packets input, 45219773963432 bytes, 0 no buffer Received 2151339180 broadcasts (1552880120 multicast) 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored 0 input packets with dribble condition detected 105941741381 packets output, 95235736709717 bytes, 0 underruns 0/88,231,052,239

This number is rather less than 1%.

Well, at least a billion times less than one percent:-)

I regard a 1% error rate on a LAN as a very high error rate.

The above was from the very first port that I checked. They will all be about the same.

Reply to
Bod43

Hi Scooty,

can you check the SFP module , this is Orginal Cisco or Cheaper form China product , this is some time is SFP problem ,

can you type the

1=2Eshow int status .please let me know SFP prot status . 2=2EShow idprom int giga

I will easy know what happen

Ryan at optech.com.tw

Ryan Ho

Scooty =BCg=B9D=A1G

Reply to
OPTECH_GBIC

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