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Level 7

Error: Server returned unroutable private IP address in PASV reply

please im having issues with my home server where is will disocnnect after some time both http and ftp.

here is a log if it of any help

Status: Resolving address of mymun2.25

Status: Connecting to

Warning: The entered address does not resolve to an IPv6 address.

Status: Connected, waiting for welcome message...

Reply: 220 Serv-U FTP Server v15.1 ready...

Command: CLNT on behalf of

Reply: 200 Noted.

Command: AUTH TLS

Reply: 234 AUTH command OK. Initializing SSL connection.

Status: Performing TLS handshake...

Status: TLS handshake successful, verifying certificate...

Status: Received 1 certificates from server.

Status: cert[0]: subject='C=US,ST=WI,L=Helenville,O=Rhino Software\5c, Inc.,OU=Software Development,' issuer='C=US,ST=WI,L=Helenville,O=Rhino Software\5c, Inc.,OU=Software Development,'

Command: USER friends

Reply: 331 User name okay, need password.

Command: PASS ******

Reply: 230 User logged in, proceed.

Command: SYST

Reply: 215 UNIX Type: L8

Command: FEAT

Reply: 211-Extensions supported

Reply: UTF8


Reply: CLNT

Reply: CSID Name; Version;

Reply: HOST domain



Reply: PBSZ

Reply: PROT

Reply: CCC

Reply: SSCN

Reply: RMDA directoryname

Reply: DSIZ

Reply: AVBL

Reply: EPRT

Reply: EPSV

Reply: MODE Z

Reply: THMB BMP|JPEG|GIF|TIFF|PNG max_width max_height pathname


Reply: SIZE

Reply: MDTM


Reply: MFMT

Reply: MFCT

Reply: MFF Create;Modify;

Reply: XCRC filename;start;end

Reply: XMD5 filename;start;end

Reply: XSHA1 filename;start;end

Reply: XSHA256 filename;start;end

Reply: XSHA512 filename;start;end

Reply: COMB target;source_list

Reply: MLST Type*;Size*;Create;Modify*;Perm;Win32.ea;Win32.dt;Win32.dl

Reply: 211 End (for details use "HELP commmand" where command is the command of interest)

Command: PBSZ 0

Reply: 200 PBSZ command OK. Protection buffer size set to 0.

Command: PROT P

Reply: 200 PROT command OK. Using private data connection.

Command: PWD

Reply: 257 "/" is current directory.

Status: Current path is /

Command: TYPE I

Reply: 200 Type set to I.

Command: PASV

Reply: 227 Entering Passive Mode (192,168,1,103,175,200)

Error: Server returned unroutable private IP address in PASV reply

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2 Replies

This is a VERY common situation with new FTPS configurations, Serv-U or otherwise.  In fact, we spend a while on it in the official Certified File Transfer Professional program.  (See​ for a quick video segment on this.) 

As josh.p mentioned, there is an explicit feature in Serv-U to tell your server use the "external" IP address of the server in the PASV response.  In fact, Serv-U's implementation includes options that allow you to only turn this on when using FTPS (i.e., when the returned address is hidden from firewalls) or only use it with specific addresses. 

Also, many FTP clients are now smart enough to ignore "unreachable" addresses from FTPS PASV responses, and to just try connecting with the same IP address used for the control channel.  If you find yourself up against this wall with OTHER people's (non-Serv-U) servers, you might want to see if a different FTP client would help. 

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Level 12

The issue is that the server is behind NAT, probably a router.

The client cannot connect the data channel, because the the server tells the client "I am listening on this IP, and this port".  Those are actually the internal NAT addresses, not the externally accessible ones.

You need to do 2 things.  First, tell serv-u to advertise the external address.  Secondly, you need to make sure the router forwards those requests to the proper machine.

Network address translation - Wikipedia, the free encyclopedia

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