FTP pasv reveals issue with port forwarding?

[airvpnclient 13]

I have been working on setting up an FTP server on my RPi box (Debian Jessie/Openvpn-2.3.4-5).  I followed the instructions found in the forums to forward a port to the listening port 21 and then open a range of high ports for Passive connections from the server to the clients.

 

My understanding is that in passive mode, the connections are all initiated by the server and so should pass through the standard Iptables firewall rules established by Eddie.

 

It all seems to be working but when testing a download, I get occasional disconnects, that reconnect an the following message in the FTP client:

 

Server sent passive reply with unroutable address 10.5.1.101, using host address instead

Is this a problem?

 

The client seems capable of recovery and there is no sign of issues (except IPV6 rejects) in the server logs.

[airvpnclient 13]

Well FTP working as advertised!  Just tested by uploading a 1.2 GB folder and all went well and it all got delivered i about an hour @ 800+Kbps.  Not sure where the choke point is, but likely inside my house, since I get 10Mbps up.  Maybe hitting CPU encryption bottleneck.