Ubuntu: FTP to my Ubuntu machine kills my network



Question:

I'm having a problem transferring files between my Ubuntu server and other machines with FTP.

Basically, if I initiate an FTP request from my Ubuntu to my Mac, it works fine. But if I make a request from my Mac to my ubuntu machine, the entire LAN crashes, and I have to reboot the router to fix it. I have experimented with what triggers this. FTP from my Ubuntu to other machines works. FTP from my Mac to other machines works. But any FTP request to my Ubuntu from any machine crashes the network.

To sum it up, if my Ubuntu receives an FTP request, my network dies, but it can initiate them just fine.

Even more, if I make a git pull request from my Ubuntu repo, the network crashes. But Ubuntu can push/pull just fine to/from my Mac. I've already been told this is likely a router issue, and I'm fine with accepting that. However, it's just odd that the issue surrounds my Ubuntu, and only when receiving FTP connections. so I'm asking if there is something that could be wrong with the machine, instead of the router.

I have even upgraded to Ubuntu 14.04.1 to see if there was some outdated package, but the problem persists.

I'm completely at a loss with what detail specs to offer, so if any other info is need, let me know.

I am using a Linksys E2500 router. It's about a year old, and I've never had issues with these routers before.

UPDATE:

After some more tinkering, I realized that FTP works fine. SFTP is what is crashing my network. I have openssh-server installed already, so I'm wondering if there is some other package that needs to be setup to allow the Ubuntu server to receive SFTP connections.

Since this problem appears not to match the original stated, I made a new thread:

SFTP to local ubuntu server crashes network


Solution:1

There is nothing wrong with your network, it's not a bug, it's a feature of TCP/IP: let's use full available bandwith, and it saturates your network easily (router gets too busy).

You need to embrace Quality of service (QoS), read about it and configure it. There should be related options in your router. Take a look at page 28 in the Linksys E2500 user manual.

Anyway, this approach might not solve your problem because QoS rules may be applied in traffic being routed between LAN and WAN but not on traffic being switched over LAN.

My recommended approach is to limit FTP bandwidth.

If your [S]FTP client has bandwith limit option, use it. Here is a screenshot of WinSCP taken from the internet:

WinSCP transfer dialog

You can see the option on the bottom right corner.

If your client does not have such option, limit server bandwidth. I have not done that myself so I can't guide you step by step, but I can point you to a configure FTP bandwidth limit tutorial.

Please keep in mind that if you are using SCP, SFTP or any SSH-related transfer, your port will be 22 instead of 21, so you'll need to tweak your configuration accordingly.


Solution:2

OK, I could tell you to try another git protocol, but this would be only a workaround.

If I were in your place, I would connect the Mac and the Ubuntu through a vanilla Ethernet hub and see what happens with a sniffer program like wireshark. Maybe your Ubuntu box emits strange Ethernet packets in some situations, maybe your route between the wireless network and the wired fails in some situations. Doing this, I would be able to state where the problem is: router or Ubuntu box.

I hope this helps, but unfortunately, I think I can't go further.


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