Server sent passive reply with unroutable address. Using server address instead

Router 1 connected to Internet – having External IP & internal 192.x.x.x

Router 2 connected to Router 1 – having WAN IP as 192.x.x.x & LAN IP address as 10.x.x.x

WD MBL is connected to Router 2 with an IP address in the range 10.x.x.x

I have forwarded a Port A in Router 1 towards Router 2 & then the same Port A is forwarded to PORT 21 in Router 2 towards the MBL IP address

I have also forwarded Ports 5000-6000 (to be used for Passive Mode) in both the routers

I can easiy access the WD MBL within the LAN using it’s local Ip address … NO issues at all

I can also access the WD MBL from outside the LAN (means internet) using an external IP address of Router 1 and using the Port A … the connection goes through as well BUT I receive " Server sent passive reply with unroutable address. Using server address instead" And it shows up the external Ip address of Router 2 with a port number within Passive Mode range … I can do all the transfers but still confused why this error is coming up … !!!

Kindly advise what is still wrong in this ???

sominaik wrote:

 I receive " Server sent passive reply with unroutable address. Using server address instead" And it shows up the external Ip address of Router 2 …

Because, by definition, IP’s in the range 10.x.x.x are unrouteable on the internet.

I would assume that Router 1 (the Internet-facing router) would need to run an FTP ALG in order to prevent that error.