SM on wrong AP - Known good APs missing from SM AP eval -- returns with rescan

We have SMs that are on the wrong AP.  They are on the secondary color code when they should be on the primary.  AP eval shows only one AP, the secondary that the SM is currently using.  Hitting "rescan" drops the link, finds both APs, and connects to the correct primary AP color code.  Now both APs are listed on the AP eval screen.  Rebooting the secondary AP does get the SM to find and connect to the primary AP but this is not an acceptable solution, nor is manually logging into each SM and forcing a rescan.  It is not clear the exact sequence of events that causes this but every month we find many SMs on the wrong AP.

This morning I just found a dozen SMs this way.  80% of the SMs were on one AP even though most should see both APs that partially overlap the SM areas.  For example, one SM was connected to a -76 secondary AP with no other AP listed in the eval screen. Hit 'recan' and now that SM sees two APs and is connected to the primary AP with a -56 signal!

We have this happening all over our network. I can confirm this on 13.4.1 on both 100 and 430 series radios. I can confirm this on 450 radios running 15.1.1.  This has been happening for more than a year.  Are we the only one seeing this??!!  Does no one use color codes to provide failover redundancy for SMs?  I reported this in the "other PMP" forum and Hardik Patel of Cambium said this was fixed on 450 release 14.2 and that they have not seeing this on 13.4.1 for the older radios.

These APs are on different non-overlapping frequencies.  The SMs have excellent signal at 4x or 6x modulation when on the primary AP they are designed to use.  APs have the subscriber color code rescan set to 10 minutes after 1 minute of idle. Can the SMs not get 1 minute of idle over many days or weeks?  Do we need the idle timer to go less than 60 seconds?  Do we need another algorithm to allow SMs to find the best AP?

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Hi Paul,

You made reference to a couple different issues in your post, so let me address them individually:

1) Regarding a fix for the issue you're now seeing having been released in 14.2, we did identify a nearly identical problem where some APs were not found during an AP evaluation scan, and the root cause was that we were not scanning long enough to see APs running 5ms frame with 100% reliability. This was fixed and validated in the field.

2) Regarding the issue you're seeing now, we are aware of at least one other large WISP experiencing something like what you describe, and have begun investigating this. We are hoping to find a cause and solution within the next couple months for release in 15.2

3) Regarding the idle timer for color code rescan, we have already identified and fixed an issue where certain management packets were preventing the link from going idle, which will be available in 15.2 Beta loads before release. We should have our first 15.2 Beta out in January or so. That said, customers who have always-on devices will interfere with the idle timer, so if you still don't see an improvement with the Beta code, you may want to consider disabling the idle timer. Granted, this may kick customers offline temporarily, but we don't have a plan for a more sophisticated idle scanning mechanism at this time.

We would greatly appreciate if you would open a ticket with customer support if you are experiencing issues with APs not showing up in your AP Eval scans, as the information you provide will help us accelerate discovery of a root cause. Either way, we are actively investigating this, so stay tuned!



Just a heads up, there has been a fix made in an upcoming 15.1.4 BETA release that will hopefully address issues where 1 or more APs may not appear in the AP Eval scan list. Please read my previous post as well, if you haven't already, as there were some other issues that may explain what you're seeing with respect to AP rescan.

Any more input you may have is appreciated.


Hi Al,

ETA for 15.1.4 BETA?

Hey Tuvix,

15.1.4 Official will be out soon, pending FCC approval, and 15.2 Beta should be out in the next week or two as well, and both of those will contain the fixes made to address the AP eval issue. Stay tuned!


That's sound good! :D

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