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Walkthrough Wednesdays

Automatic port synchronization (APS) on cisco phones - 7841 & 8851

I've had quite a journey troubleshooting a bandwidth issue reported by a number of branch offices - the upload being significantly slower that what the circuit guaranteed. What was thought to be either an ISP issue or a possible issue with copy past config on our end, eventually ended up being an issue with the phones passing through data (user jacked in straight to wall and confirmed upload speeds were normal again).

I tested various settings via CUCM on the specific user phone and found that APS (automatic port synchronization) allowed it to negotiate and rectify the upload issue. I would rather not implement so specific a change so broadly into our ecosystem if this isn't the only path (bulk phone model type update)

During troubleshooting and isolation testing, I had the user swap the cable and tada! he was showing good speeds BUT, a few moments later the next test showed a slow upload again. APS fixed the issue though. /shrug

Further details:

When testing this fix on another set of users, one of them took easy enough - adjust only the APS setting but another was not having it. The PC was registering slow uploads at the jack. So i got into the switch and forced speed and duplex. nothing. I then adjusted the speed to 100 Mbps instead of the full gig speed that was set. Tada! it worked. I then confirmed the issue I believe by going back to speed 1000 just to confirm the fix and back to speed 100. So this particular user required APS + reduced speed at the switch - which the whole site would possibly need.

Seems there's an association with 1 Gbps interfaces possibly not negotiating the way they should at the phone. I checked the documentation and if i remember right there wasn't an issue with the phones capping port speed - seemd to support 1 Gbps connections.

So i guess I got to figure out how to fix apply a fix to these phones at their site. Bulk administration for specific phones doesn't seem to be a thing in CUCM. Guess that's a scripting endeavor.

Any thoughts or advice would be appreciated! 

Nithin Eluvathingal
VIP Advocate

If you need to Set Up Automatic Port Synchronization for a group of phones you can do that from 

System Enterprise Phone Configuration
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