Primary Hub disconnecting/unavailable in IM

Products

• DX Unified Infrastructure Management (Nimsoft / UIM)
• CA Unified Infrastructure Management On-Premise (Nimsoft / UIM)
• CA Unified Infrastructure Management SaaS (Nimsoft / UIM)

Issue/Introduction

I'm migrating environments, and the way I'm doing it is pointing my old hubs to my new primary hub, then moving robots off the hub.

For whatever reason, in IM, the Infrastructure Manager (IM) won't connect to the primary hub unless I restart the primary hub. Whenever I do that, it's good for a few minutes, then back to the original state. QOS & Alarms keep flowing and working, and accessing other hubs works (and navigating to other hubs).

Architecture is as follows:
Secondary hubs are the tunnel servers, and the primary hub is the client. Hubs are on 9.38 for the new build, and 9.31 for the old hubs. The secondary hubs are attach queues, and the primary hub is a get for the queues. 

Is there some sort of tunnel limit I can have in an environment? I'm not at the subscriber queue limit (when I do list subscribers, its at 21).

Environment

• Release: 20.4

Resolution

UIM hub subscriber limits and how to monitor the count of subscribers
https://knowledge.broadcom.com/external/article/33649 

***Alarming on the number of subscribers***

Using the hub Raw Configure you can add a NEW key and value to set the configuration parameter in the hub section to alarm when the number of subscribers reaches a specific value (see below).

subscriber_max_threshold
Specify the number of subscribers that must be reached to generate an alarm, e.g., 50.

subscriber_max_severity
Specify the severity of the max subscriber alarm above. This value is numeric.
 
Alarm severity values:

5 is Critical
4 is Major
3 is Minor
2 is Warning
1 is Informational

Customer ultimately set the tunnel connection limit down to 25 and the hub/tunnel/connections stabilized.