FTP Fails

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Nov 29th, 2007
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This is one of the interesting issue which i am facing. Whenever my client tries to send a file less than 1kb, the file is transmitted successfully over ftp, but for files greater than 1kb, the files are not being transferred, instead a 0 kb file is created on the destination server.

1. Link utilization is fine

2. No crc's etc on the link.

3. server settings are perfect.

4. MTU settings default to 1500 for the WAN link.

Kindly advise.

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lgijssel Thu, 11/29/2007 - 04:54
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This can hardly be anything but MTU related.

Try what happens when you use the command " ip tcp adjust-mss 1300" on the LAN interface of your Internet router.



vatsey.sharad Thu, 11/29/2007 - 05:26
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Well nothing seems to change, even after implementing "ip tcp adjust-mss 1300" ftp for large files is still failing.

lgijssel Thu, 11/29/2007 - 05:35
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Two other things to check:

-Any Policies or route maps there that might be messing with the df-bit?

-Any restrictions (for the user) about the file size on the server?

Are you able to upload files locally?



Wilson Samuel Thu, 11/29/2007 - 07:06
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Are you certain that its not related to the hosts i.e. Server and Client.

Interesting issue, please keep us posted about the matter.


Wilson Samuel

stephen.stack Fri, 11/30/2007 - 08:13
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Just jumping in and taking a guess here. My previous experience of FTP not working are related to MTU and MSS settings on both internal and external Ports. Are you using DSL as you WAN connection. If so then please apply the following.

Interface fa0/0

description ***INTERNAL INTERFACE***

ip address

ip tcp adjust-mss 1452

no shut


interface fa0/1

description ***EXTERNAL INTERFACE***

ip address

ip mtu 1492

no shut

If this does not work, then let us know how your router is configured and what type of wan links are being used.

HTH, Please rate if it does.



Danilo Dy Sun, 12/02/2007 - 06:20
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Can you tell us more on the following?

- FTP Client apps and version

- FTP Server apps and version

- FTP Server OS and version

Also check the FTP server settings and the destination folder settings.




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