Using 10/half on a gigabit port not working

[Marty O'Connor]

We recently upgraded the switch to which an old security device was connected.  It worked fine on the old switch's FastEthernet port, which was configured for speed 10 and duplex half, as that is what the device required. The new switch is a 3560X with all Gigabit ports, but the security device's port, also configured with speed 10 and duplex half, does not connect properly.

As a temporary test, we daisychained another switch that has FastEthernet ports, and the security device works again.

Is there anything else that needs to be added to the configuration, when using Gigabit ports at 10/half?

[cadet alain]

Hi,

Gig ports can't work in half-duplex on Cisco devices.

Regards.

Alain

Don't forget to rate helpful posts.

[Marty O'Connor]

My understanding is that for gigabit speeds, you must use full duplex, but for 10 and 100 megabit, you can still use half duplex.

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SY/configuration/guide/configuring_interfaces.pdf

[Marty O'Connor]

OK.  I found something else.  In...

http://www.cisco.com/en/US/docs/switches/lan/catalyst3750x_3560x/software/release/12.2_58_se/command/reference/cli1.html#wp2233221

there is this snippit...

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Note Half-duplex mode is supported on Gigabit Ethernet interfaces if the duplex mode is auto and the connected device is operating at half duplex. However, you  cannot configure these interfaces to operate in half-duplex mode.

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I interpret that to mean that I should configure the port as duplex auto and it should successfully run at half duplex.  I will update this discussion, after I've tried that.

[markeelen]

Hi Marty,

     I work in the security industry - spend a lot of time with speed/duplex issues with various security manufacturers not implementing auto negotiation by the standards. My understanding is this:

A 10/100/1000 autonegotiating port will try to negotiate in the follwoing sequence

1000 full duplex

100 full duplex

100 half duplex

10 full duplex

10 half duplex

If the other end does not negotiate, the port negotiating will default to 10/half ie the lowest possible - this causes speed / duplex problems if one end is set auto and the other is forced into anything other than 10/half.

The reason I can tell you this is that one particular video codec manufacturer still produces video codecs that are forced to 10 / Full and these are installed onto the networks we install, which are normally 10/100/1000. What happens is known within our industry as the ****** (insert manufacturers name) Walk - When you watch the video and someone is walking down the street, they walk...stop....walk....stop....walk....stop....continue to infinity........

What is happening is one end is forced to 10/full the other end tries to auto negotiate, but defaults to 10/half - Collisions and confusion abound. Then the manufacturer has the audacity to blame the network!!!!! Grr.

The 3560X has 10/100/1000 ports. I would set the security device to the fastest possible (100/full or 10/full) and configure accordingly on the 3560.

As to why you are having problems, i cant say. If the security device is set at 10/half, it should just plug and play.

You could set up a SPAN port on the switch and analyse the packets. That way you would be able to see what is going on.

I say that, cos I sat all morning this morning just watching packets between a server and a client trying to pick out the one packet that keeps locking up a video stream. 250000 packets per minute - Needle - Haystack........Glad to say I found it at lunchtime....Yay.

Hope that helps, if you want, PM me with the manufacturer.

Cheers

Mark