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Strange FTP issue

LordFox
Grafter
Posts: 211
Thanks: 6
Registered: 10-03-2008

Strange FTP issue

For quite a while now I've had an issue uploading files to my web host (Bluehost) by FTP. It's not often I upload so I've not got around to investigating until now.
If I do it from most of my (Windows 7) PCs, roughly 80% of uploads don't work. That is: FileZilla or DirectoryOpus say the transfer worked, but on the FTP server the uploaded file is too short. There are no errors given from the FTP process.
However, if I do the upload (still with FileZilla) from my virtual Windows 2003 Server running on my HP server in the loft, it always works.
My network is a little complex, but suffice to say that the PCs are NAT'd, one of them with static NAT, while the HP server is effectively in a DMZ but with a public IP address through a transparent bridging firewall. That's all done through a Cisco Router and a L3 switch. I have a /29 IP block.
Now, I thought that since all the (NAT'd) PC's have the issue and the HP server does not, that it was probably the config on the router for the main LAN VLAN. Probably still is, but I cannot see anything wrong. It's not like it's complicated (not for simply allowing FTP anyway).
So, to test that, I put my main PC onto the same VLAN as the HP server and gave it a public address and the relevant default route. It should have been exactly the same as the HP server now in terms of internet access.
That made no difference. Even though the PC went through exactly the same route to the internet as the HP server, with a public address and no NAT'ing, the FTP uploads still most often came up short from the PC (with no error messages) while they worked from the HP server.  Huh
Colour me stumped!
I can't quite get my head around the FTP client saying that the upload succeeded, while on the FTP server the file size is too short. Small files end up zero bytes. Then once in a while it works OK. Go figure...
Any ideas folks?
1 REPLY
LordFox
Grafter
Posts: 211
Thanks: 6
Registered: 10-03-2008

Re: Strange FTP issue

Just to add:
Active and Passive modes - both 'work' but make no difference to the issue.
FileZilla's 'Network Configuration Wizard' reports no problems and says things should work.
I have disabled TCP Offload, IPV4 Offload and Large Send Offload on my NIC. That see,s to have made no difference
Files can be short by a few bytes up to 100's kB. I thought there was a pattern of 65536 at one point, but that was short lived.
Using Window's own ftp on the command line seems to give less of a shortfall; might just be coincidence.