SMs Suffering Hung Sessions

Hey all,

We have been experiencing SMs randomly dropping traffic for over a year now and I was wondering if there was a roadmap to getting this corrected.  Essentially the SM stops passing traffic, but maintains connectivity to the AP; from the customer's perspective they have no Internet and call in to complain.  We find that the SM's interface is not reachable directly via IP or through the AP and no longer responds to SNMP, but is still connected in session to the AP itself.

Dropping the SM session from the AP magics up a recovery and everything works normally again after that.

We were hoping 15.1 would have a better fix in place that the 14.x software, but they are still ongoing even as of thing morning.

Any thoughts?

this is exactly what I was describing in my post. Glad to hear it is something more than my imagination.

Hi Jacob Barnard, Can you send CNUT capture of AP when you see that SM’s are not accessible/passing traffic. Next drop the session of the affected SM, once the SM is reachable and passing traffic, send CNUT capture of this SM as well. Please send these capture to solutions AT cambiumnetworks DOT net Thanks,


While we investigate this issue, there is a workaround Ping Watchdog, enable this feature.

Refer this page for details

Please also report the results of link test to the affected SM.

Bringing an old topic back to life as I believe I had this same issue last night and wish I would have cleared the sessions before just rebooting the AP. Has there been any development on this or are people still experiencing this? I'm hesitant to do the ping watchdog option, would rather it just not happen.

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Bump.  I'm actually seeing this worse on 15.1.3 vs 14.2.  

I have one particular case where the SM would hang and then drop on its own relatively frequently, but now it hangs and I have to manually drop the session since I moved the AP and SM from 14.2 to 15.1.3.  


It's not a network wide thing as far as I can see.  The use case in question is pretty basic, no NAT, no PPPoE, just management VLAN and otherwise is basic bridge. 

It runs pretty steady at 8x modulation, but LOS is not "perfect" either with some fresnel interference when the leaves are out.  

Do we know anything about the conditions that cause these sessions to hang?