Calico network issue, TCP answer packages not coming back into Pod


my Kubernetes app has to connect to an external MS-SQL Database.
The MS-SQL is working all good. Other Application are using it without problem.

So I created an endpoint in Kubernetes named “mssql” and tested the reachability from the pod. No problem here, I can reach the SQL Server on port 1433.

So the “real” sql connection has to work?
Nope. Not for me.

The error in my app is “Timed out”.

With wireshark, I can see the packets coming in on 1433 and the answer going out. Looks correct.
But the answer packages never arrive on the pod.

Looking at the attached screenshot, you can see the wireshark capture.

So it has to be a network issue. I am using Calico, but when it comes to network configuration, I am completely overchallenged.

Can someone please advise me how to configure the network correctly, so the SQL connection works?

Some information: - SQL Server - Linux machine holding the Kubernets Cluster master AND nodes - Kubernetes Pod Network - Pod, which is trying to establish the sql connection

Thank you in advance!