Unified Agent (UA) is no longer connecting via UDP, instead it is using TCP.
While UA is connecting, it sends an ICMP packet of 1500b in size. This is to verify the reliability of the connection and define the viability of using UDP in its connection.
If the packet is not responded back, UA will connect using TCP.
In the images below is a comparison of failing and successful scenarios for this setting. First the success and then the failure.
Check packets 39~40 for Ping results, and packets 42+ for results.
Check item 71 for ICMP packet, and results on items 92~94.
Check the customer's architecture to see if ICMP packets of size 1500 are allowed to be sent or received to our IPs. Try doing manual pings to see if they go through.