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FTP Issue - Works from one place, fail form other place



I have an FTP file transfer issue.

Client is accessing an application in Data center to put some files via FTP.

When he access from office it works fine. As he access from home (Office LAN is extended to home through wireless network, meaning he gets same IP etc while at office or at home so same policies are applied on his laptop)(setup is Date center <<----->> Branchoffice <----> wireless bridge <---> wireless bridge <--> Home) it doesn't works.

Find attached the capture for both situations. I have included only some packets and removed other extra.

Please share your views.

Thank You.


manish arora
Frequent Contributor
Frequent Contributor

It appears to be an MTU issue, looking at the wireshark captures , you can see the FTP server is sending packets with Donot frag Bit set on. That is the reason that when the client is connected to the office network the MTU is good enough for transfer where as the wireless bridge connection as a lower MTU and is dropping the packets.

Try ping -f -l 1500-1300 ftp-server from client machine and see the optimum MTU for the path. Then set the MSS on the clients laptop to the successful MTU and give it a try.

if that doesn't work then we can look more into it and get tcpdump from the server side.


If indeed is an MTU issue you may use one of the following tools to help you out

  1. ip tcp adjust-mss on the interface
  2. policy route-map to remove the df-bit

Configuration would look like

route-map TEST

match ...

set ip df bit 0


ip policy route-map TEST

Hope this helps you out

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