Windows Server 2016 FTPs behind a load balancer.

T

Tom Thi

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I'm having an issue with IIS 10 FTP server.



The host is Windows Server 2016 running a FTP server that is behind a Elastic Load Balancer in AWS. I know that when using a ELB you have to use passive mode. On the FTP server side under the FTP Firewall Support I've set the specific data channel port range. In the FTP Service I have put the Public IP of the ELB in the FTP Firewall Support IP address field.



The port range I've configured is 4100-41500. From the client side I can connect but it hangs when it goes to get the directory listing. In the IIS Console I can see active connections. I've tried using FileZilla and Cyberduck, neither of them seem to work. I have also specified passive mode in the connection configuration.



When you run a Netstat -A I can see the foreign host IP of the ELB but the port it's going back out on is not in the range I set in the IIS Firewall configuration.



The Security Group for the Windows Host allows Port 21 inbound and outbound is not being restricted. I have listeners on the ELB configured to forward all 21 traffic to the Windows host.



Outbound traffic is not being blocked on any subnet.







Thanks.

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