Hi,

I've a very peculiar problem about scp and sftp. I can successfully ssh to my box, run commands etc. But when I scp or sftp, I can only do downloads and not uploads. When I try to do an upload, the file is created on the remote site with 0 byte, while the local "progress bar" indicates some non-zero percentage (sometimes 8%, 20%, depending on the file size) and then stallled.

Note that the above case happen when both machines are behind a NAT firewall each. When I try to do that in LAN (to the same ssh server, but different client), it works.

Now, the funny thing is, if I change the MTU size to 500 (from 1500) at the client side, there's still stalling, but nevertheless, the file is copied. At the server side, the MTU is still 1500.

Can anyone explain why this is so? I googled around for this solution, but I don't know why this helps...

What NAT firewall are you using? I had this problem with the last fire wall I through out my window... Kidding... It is now on my shelf.. The police officer was going to get me for littering if I didn't pick it up...

The server is behind a US Robotics broadband router, while the client is behind a ipchains firewall.

The USR router is blocking ping.