Cisco 3750 manually set full duplex 100

[lmuller3]

We have a Cisco 3750 with the speed and duplex set to Auto. This port communicates with a Harmonic 9101 fiber optic converter to Comcast. This converter communicates at full duplex and 100.

We are trying to manually select Full Duplex and 100 rather than the Auto setting. When we set the port manually to these two settings the port will not communicate (no green light on the port). When the port on the Cisco is set to Auto for Speed and Duplex we generate a high level of errors. Is there another setting in the switch that may prevent a manually set port from communicating at Full duplex and 100?

Any assistance is appreciated

 

[lerdalt]

Sounds like a cabling problem to me. I have many 3750's and I haven't had a problem like this unless there is an issue with either the cabling, or the speed/duplex setting on the other device.

You might want to see what happens if you set it to 10/half, just for kicks.

What kind of errors do you get at auto/auto? Did you see what the port detected for speed/duplex?

 

[ADB100]

This has been discussed recently and is due to Auto-MDIX.

http://www.tek-tips.com/viewthread.cfm?qid=1509668&page=2

When you hard-code the interface it disables the Auto-MDIX feature so you will need to use a cross-over cable. With Auto-MDIX enabled it 'corrects' cabling issues where with older switches you would have needed cross-over cables.

Andy

 

[lmuller3]

Comcast ran a test beginning at the end of our patch cord that plugs in to the router and that ran clean with no errors. I did set it to 10 and full duplex and still did not communicate. Comcast states the Harmonic 9101 is full duplex and 100. We detect full duplex and 100 on the 3750 when we have it set to Auto. The converter has been replaced and there is no setting on the converter to change. Comcast has indicated that the manual setting of Full Duplex and 100 has resolved this problem in the past with other customers.

We see no errors on the port in the Cisco log. Comcast only gets errors that read hardware issue on approximately 10% of the packets.

 

[lmuller3]

The Harmonic 9101 has a cable switch that allows the converter to be switched from a regular cable to a cross over cable. When we made the hard code we waited a couple of minutes to see if the port would light up on the Cisco then we flipped the switch on the Harmonic and waited a couple of more minutes and the port still did not light up on the Cisco.

We will try the crossover cable to see if that works.

 

[burtsbees]

Why did you want to hard code the 3750 in the first place? If it ain't broke, ...

Burt

 

[vipergg]

AB100 already gave you the answer , you are using mdixwhich corrects for an improper cable and that only works if the setting is auto , if you need to hardcode then you need to get a different cable , if you are using a straight thru right now then you need a crossover instead and then you could hardcode or vice versa , if it is a crossover currently change it to a straight thru.