[Solution] Speed / Duplex auto-negotiation fails between Cisco and Tandberg

In the last weeks I was working closely with a Cisco Telepresence team to identify a issue regarding poor performance of the video systems. We did find pretty quickly the issue as being the failure of auto-negotiation of Speed and Duplex on the connection between Cisco switch port and Tandberg endpoint devices.

This was the easy part. We though it will be fixed in minutes, but after a few days we did recognized that there is something we do not understand. We did change the settings everywhere to have auto-negotiation on, but we still had problems. For example with Cisco and Tandberg ports set on auto-negotiation on both sides, I’ve seen the most uncommon results:
– Cisco 1000Mbps – Tandberg 1000Mbps = negotiation 1000Mbps / Full
– Cisco 1000Mbps – Tandberg 100Mbps = negotiation 1000Mbps / Full on Cisco + 100Mbps / Full on Tandberg
– Cisco 100Mbps – Tandberg 100Mbps = negotiation 100Mbps / Half on Cisco + 100Mbps / Full on Tandberg

These are just a few of the strange results that we got. Myself as part of the network team I turn my attention to search bugs in IOS, configuration issues, faulty hardware. The Telepresence team was doing their job to search on their systems. Nothing was working.

We turn our attention to TAC engineers. They did try to simulate in a lab environment our problems, but failed. Their system were not having this kind of issue. Internet, search engines and boards could not help as well. I was about to think that we are somewhere in the Bermuda triangle and we are the only one with this kind of problem.

Then the solution came from a Cisco engineer when we least expect it. I quote from his e-mail in which he gave us some suggestion to try:

Are you aware that Tandberg endpoints running newer versions of software 
need to be rebooted before changes to speed settings take effect? 
This can sometimes cause confusion.

We stopped for a second and ask “Did we reload any Tandberg device during troubleshooting sessions?” The answer was “No”. After reload all devices, one by one, everything was working expect a few devices.

We discovered that these Tandberg devices didn’t want to auto-negotiate because of lack of a Cat6 cabling. It seems that all 8 wires need to be there and connected. So, if you have a cable that is patched to transport data and telephony for example to spare some wires, then you may be in trouble.

Why did I add this thing here? For sure it will bring some ironic smile on some faces, but I like to learn from my mistakes or from not paying close attention to some small line in the documentation. OK, if I made you laugh it’s fine, but the reason of this article is different. When I did search Internet for possible solution, I could not find anywhere a line with “reload the damn Tandberg device after you modify Speed / Duplex” settings.