Upgrade past 15.1.3 having sync output issues with remote AP's


Last night I sent out an update for AP (450 3.65GHz) + SM's to v  I started at v15.1.3 and while the upgrade went OK, and all SM's came back at, I have an issue with a remote site fed through it.  The AP at the Remote Access Point  (FSK v11.2) connected with a sync cable now says, "Error, No Sync" but SM's were still registered.

I rebooted that remote AP and the SM's never come back.  Same message, "Error, No Sync"

I rebooted the newly upgraded 450 AP with no luck.

I downgraded the SM feeding the RAP to v15.2.1 but the same condition applies.  I downgraded the SM back to 15.1.3 and the issue is gone and operation is normal.

This is not the only site I had this issue with.  I see the same senario with a 450 2.4GHz AP feeding another FSK AP with a sync cable attached.  Same condition, "Error, No Sync" and SM's continue to stay registered.  Downgrading the SM feeding the RAP to v15.1.3 fixes it.

Cambium, any thoughts on this?

I opened a support ticket about this issue also.

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This is actually an issue another customer reported recently, and you've identified the exact scenario that causes it.

We had put in a fix in 15.2 which allows 450 remote AP's sync to be driven more reliably by a 450i SM/BHS, which has been somewhat flakey with long cable runs since 450i was released. Unfortunately, this inadvertently caused the issue you're now describing.

We have identified a fix for this in firmware, which will be added along with a new GUI option tio choose the remote AP type (FSK or other) to ensure this will work on both platforms. I will have to get back to you on what SW release that will get into, but for now I think it's most likely to be 16.1, due out in the next few months.

In the meantime, the workaround for FSK remote AP is to ensure the source is running 15.1.5 or older. For anything else as remote AP, 15.2.1 or later is recommended.

Thank you for opening a ticket, as it's the most reliable way to get your issue identified internally.


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Ok, I verified this has already been fixed in firmware, but needs some software work for the feature to be displayed for configuration, which we’re working on as I type this. Keep an eye out for the 16.1 release (or Beta if you’re in the Beta program, which would be available sooner), and you should see some notes regarding this issue and how to resolve it.

I suppose a warning to operators downloading firmware would be helpful.  Or update release notes now that you found a bug.  Right now it says, "No known open issues are identified in System Release"


Great suggestion FVI. I will get the release notes updated to reflect the finding of this issue.

If the next version doesn't resolve the Ethernet Tx Stalled error (only occurs with SMs connected to a Medusa and in NAT mode), it should be explicitly listed, as well.