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Duplexing issues with C20s

I've encountered a problem today with a couple of C20s and duplexing errors.

As we run fibre everywhere, auto-duplexing is not an option so run everything at 100/full duplex and all our endpoints have this hard set.

Today we've had a couple of C20s boot up and in the diagnostics they are giving an error saying that there is a duplex mismatch between the unit and the nearest CDP device.  When I click the "system" link for the C20 (contained within the error message), it reports as 10/Half, but in the network settings it's set to 100/full.  The "CDP" link reports as 100/full.

During conferences, packet loss is experienced as would be expected for a 10/half link.

So my quesiton is this - why would the C20 boot up at 10/Half even though I've got it hard set to 100/Full? And why would the network settings still report that it's hard set to 100/full, even though it's operating at 10/half?

Software version on all affected units is TC6.3.  I haven't had much of a chance at troubleshooting yet as all affectecd units are in conferences for several hours, but I thought I'd put this out there now in case sombody has seen this behaviour before.


Re: Duplexing issues with C20s

Quick note to add:

I saw bug ID CSCub03016:

"The output of the xStatus Ethernet duplex setting on an EX90 when running TC5.x as well as latest TE6 alpha release is incorrect. When it is configured for half it still shows full."

This sounds somewhat related, but it also says it's resolved in TC6.0 so I don't think it's the same issue.


I'll also note that we have several C40s, C60s and EX90s running in the same configuration and thus far none of these have presented the same symptoms.

Community Member

Re: Duplexing issues with C20s

Check your media converter. There may be dip switch flipped not allowing CDP or auto negotiate to function properly. I work with a large number of sites connected via fiber and that is usually the issue.

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Re: Duplexing issues with C20s

Definitely worth a look - thanks!

Re: Duplexing issues with C20s

OK, update on this:

For the first C20, we had the media converter checked and the dip switches were set correctly to 100/force and has all other dipswitches set to their defaults as per all our other, working units.  I haven't been able to reboot this one as the room is being used.

For the second one, it's in another state so I can't look at the media converter, but after the call finished I rebooted it and it came up without the dublex problems, so I can assume the media converter is OK.

It might have something to do with the codec booting up before it gets a network connection (one of them has a funny AMX setup, the other one is on a trolley that gets rolled out and plugged in only when it's going to be used).

Any ideas?

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