I have a web server hosted on AWS sending email via an email server hosted in a separate data center. I can telnet into the email server with no issues from a server outside AWS but when connecting from my AWS web server I have two issues.
The initial connection often gets stuck in a series of re transmissions after an initial spurious re transmission immediately following the syn/ack. You can see this at the beginning of the trace. This issue is duplicated when I send emails. The initial send hangs until a connection is made.
At the end of the trace you can see frame 13198 on the web-server acks's sequence 8040907. However the very next frame again begins another series of re transmissions. You can see the ack for 8040907 on both the web-server and the email server trace I've included below. The acks are getting lost but I'm not sure where. I'm connecting directly from the public ip of the aws web server to the mail server and not through a load balance.I have also opened the inbound ports in the security group to include the port I'm using to connect to email as well as allowing in all ICMP traffic. Would greatly appreciate any insight.
webserver trace 10.2.2.2 https://www.cloudshark.org/captures/d17da6802b39
email server trace 10.1.1.1 https://www.cloudshark.org/captures/d6c1e750ddf8
asked 22 Dec '16, 22:23
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