I am having a bit of a quirk with my IIS server. I'm running my IIS with 2 sets of IPs configured, one in the 192 range and the other in 172 range.
I then have multiple apps which will talk to this server for information. Server has no AV or firewalls configured.
I noticed that my apps when talking to the server on the 172 range, at random intervals, the server would just not respond. My apps would then disconnect and just try again, and every thing would be fine. This doesn't happen on the 192 range.
So what I did is on a Linux box I did a watch command and to wget a file every half second on the 172 and 192 IPs. I noticed the same issue, every once in awhile wget on the 172 range would not get through, but there is no issues at all on 192.
Thus I went around to Wireshark and did a dump. This is the last 3 packets, no other packets were received.
7010 100.871877 220.127.116.11 18.104.22.168 TCP 59619 > http [ACK] Seq=140 Ack=85242 Win=64128 Len=0 TSV=1072818795 TSER=1660246133
7011 100.872238 22.214.171.124 126.96.36.199 TCP 59619 > http [FIN, ACK] Seq=140 Ack=85242 Win=64128 Len=0 TSV=1072818796 TSER=1660246133
7013 100.873081 188.8.131.52 184.108.40.206 TCP 59619 > http [ACK] Seq=141 Ack=85243 Win=64128 Len=0 TSV=1072818796 TSER=1660246133
So this is my issue, there is a random disconnect every once in awhile. The server doesn't receive the next SYN packet.