Pfieuw...talking about loooong posts 
These issues are tricky to find especially if it is an intermittent issue. What to do to test if all is ok now? I'm not sure. I guess setting up some kind of process that generates traffic on the network just like it was a "normal" day would be best but I'm not sure how to set this up.
For the monitoring part we have been using OpManager by ManageEngine for years and I'm very happy with it. There are some plugins available for for example NetFlow. It can send notifications by SMS message and e-mail but we only created an e-mail profile because SMS a so pre 2005 I did set a notification sound to this one specific e-mail address on my iPhone so it only makes some noise when an e-=mail comes in from the monitoring system. No reason anymore to spend money on SMS messages.
ManageEngine: https://www.manageengine.com/
OpManager: https://www.manageengine.com/network-monitoring/
Customers: https://www.manageengine.com/network-monitoring/customers-list.html
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Mart
- Chuck Norris once sold ebay to ebay on ebay.
