Server sent passive reply with unroutable address

10/11/2018 6:25 PM

6/15/2020 1:15 PM

FileZilla users are unable to list to directory and receive a connection error:

Server sent passive reply with unroutable address.

Serv-U Managed File Transfer & Serv-U FTP Server

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.

1. Go to the Serv-U settings at: Global Limits & Settings > Settings - Network Settings.
2. Ensure the Auto-configure firewall through UPnP checkbox is not checked.
3. Ensure the Packet time-out is set to 300 seconds.
4. 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 you are still unable to connect, the next step is to configure the IP address Serv-U uses for its response to the PASV command so it uses the actual IP address and not the internal IP that Serv-U sees. But this should be automatically done by their NAT device.

To do this:

1. Navigate to Domain Details > Listeners.
2. Select your FTP/FTPS listener(s) and click Edit.
3. Enter the external IP address (or domain name if applicable) of your internet connection in the PASV IP Address Or Domain Name field. If you are using Serv-U with a dynamic IP address, leave this field blank.

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).

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