Hi All,
I have been facing a issue between my devices (Server and RTU device) where the communication gets initiated and immediately resets and starts the whole cycle again. I noticed that Wireshark logs showing RST, ACK highlighted in red colour and am not sure if that is the problem.
I have redundant servers and when I force the communication to other server the RTU device works fine. I did a ping check and there are no TCP timeouts between Server and RTU device. RTU is Remote Terminal Unit used for field device communication.
Below shows issue between Server 10.211.14.126 and RTU 10.211.173.119.
10.211.14.126 10.211.173.119 TCP 1434 [TCP Retransmission] 64420 → 1090 [ACK] Seq=1772 Ack=8651 Win=262144 Len=1380
10.211.14.126 10.211.173.119 TCP 1434 [TCP Retransmission] 64420 → 1090 [ACK] Seq=1772 Ack=8651 Win=262144 Len=1380
10.211.14.126 10.211.173.119 TCP 54 64420 → 1090 [RST, ACK] Seq=3152 Ack=8651 Win=0 Len=0
10.211.173.119 10.211.14.126 TCP 60 1090 → 64394 [FIN, ACK] Seq=8651 Ack=1772 Win=8280 Len=0
10.211.14.126 10.211.173.119 TCP 54 64394 → 1090 [RST] Seq=1772 Win=0 Len=0
10.211.14.126 10.211.173.119 TCP 66 64457 → 1090 [SYN, ECN, CWR] Seq=0 Win=8192 Len=0 MSS=1460 WS=256 SACK_PERM=1
10.211.173.119 10.211.14.126 TCP 62 1090 → 64457 [SYN, ACK] Seq=0 Ack=1 Win=8280 Len=0 MSS=1380 WS=1
10.211.14.126 10.211.173.119 TCP 54 64457 → 1090 [ACK] Seq=1 Ack=1 Win=262144 Len=0
After this the communication resets and gets initiated again.
Below shows working communication between Server 10.211.14.127 and RTU 10.211.173.119.
10.211.14.127 10.211.173.119 TCP 1434 [TCP Retransmission] 56669 → 1090 [ACK] Seq=1772 Ack=8651 Win=262144 Len=1380
10.211.14.127 10.211.173.119 TCP 1434 [TCP Retransmission] 56669 → 1090 [ACK] Seq=1772 Ack=8651 Win=262144 Len=1380
10.211.14.127 10.211.173.119 TCP 590 [TCP Retransmission] 56669 → 1090 [ACK] Seq=1772 Ack=8651 Win=262144 Len=536
10.211.173.119 10.211.14.127 TCP 60 1090 → 56669 [ACK] Seq=8651 Ack=2308 Win=7744 Len=0
10.211.14.127 10.211.173.119 TCP 590 [TCP Retransmission] 56669 → 1090 [ACK] Seq=2308 Ack=8651 Win=262144 Len=536
10.211.14.127 10.211.173.119 TCP 590 [TCP Retransmission] 56669 → 1090 [ACK] Seq=2844 Ack=8651 Win=262144 Len=536
10.211.173.119 10.211.14.127 TCP 60 1090 → 56669 [ACK] Seq=8651 Ack=2844 Win=7744 Len=0
10.211.14.127 10.211.173.119 TCP 186 [TCP Retransmission] 56669 → 1090 [PSH, ACK] Seq=3380 Ack=8651 Win=262144 Len=132
10.211.173.119 10.211.14.127 TCP 60 1090 → 56669 [ACK] Seq=8651 Ack=3512 Win=7612 Len=0
10.211.173.119 10.211.14.127 TCP 1434 1090 → 56669 [ACK] Seq=8651 Ack=3512 Win=8280 Len=1380 [TCP segment of a reassembled PDU]
10.211.173.119 10.211.14.127 FF 678 FMS Read Response
10.211.14.127 10.211.173.119 TCP 54 56669 → 1090 [ACK] Seq=3512 Ack=10655 Win=262144 Len=0
10.211.173.119 10.211.14.127 TCP 60 [TCP Dup ACK 98836#1] 1090 → 56669 [ACK] Seq=10655 Ack=3512 Win=8280 Len=0
Appreciate if you could provide some expertise on this. Thanks in advance and apologies for poor formatting.
