This article will guide you on ways to resolve #Server sent passive reply with unroutable address which occurs due to bad server settings or when an FTP client is behind #NAT.
#FileZilla has updated their FTP #client, and FTP over TLS is now used by default. This results in clients being unable to connect to their server from the outside network.
Make sure that you properly set up for FTP over TLS/SSL, explicit and passive ports are allowed on the #firewall and set on Serv-U:
i. Go to the Serv-U settings at: Global Limits & Settings > Settings - Network Settings.
ii. Ensure the Auto-configure firewall through UPnP checkbox is not checked.
iii. Ensure the Packet time-out is set to 300 seconds.
iv. Set #PASV Port Range is 50,000-50,009, and port forward these ports to your router.
This configures the file transfer traffic to be routed through the router and directly to Serv-U through “Port Forwarding”.
If, after this, you are still unable to connect, try disabling the "Block FTP_Bounce and FXP" option - this has been known to cause issues for some clients. To do this, follow the steps below:
1. Navigate to Global > Limits and Settings > #FTP Settings.
2. Select Global Properties. (If this is not available, first select Use Custom Settings to gain access to it).
3. On the Advanced Options tab, make sure "Block FTP_Bounce and FXP" is unchecked (which it is by default).