I've got a server running CentOS 5.5. I used the automated iptables config tool included in the operating system to allow traffic for vsftpd, Apache and UnrealIRCd.

When I send large files to FTP, even from the local network, it works fine for a while and then completely times out... on everything. IRC disconnects, FTP can't find it and when I try to ping it I get "Reply from 10.1.10.134: Destination host unreachable" where ..134 is the host address for the Win7 box I'm pinging from.

This is especially frustrating as it's a headless server, and as I can't SSH into it to reboot I'm forced to resort to the reset switch on the front, which I really don't like doing.

I am completely at a loss why it would do this, and don't even know where to begin looking for a cause. Anyone have any thoughts?

Edit: Thought I'd mention, the timeouts are global, across all machines both on the local network and users connecting in from outside.

To me it sounds more like a network issue in any switch or so. Do you have a free Ethernet port on the server which you could configure to work on any other subnet range? When the issue happens again, you could use a laptop to test the access via the second Ethernet port then. When this direct connection is working, it must be something outside of the server causing this.

I do have one I can try, but it's spotty at best. The board is ancient, and that particular port seems to have driver issues. As the machine is in use I won't intentionally break it, but I'll report here what I can whenever it happens next. In the interim, I'll turn the port on.

I was doing some maintenance on the machine and had plugged in a monitor and keyboard. While I had everything plugged in, I decided to give a large FTP transfer a shot, since I would be able to actually look around on the machine & figure out where it was breaking.

What's happening is the machine is hardlocked. Not even the numlock key on a physically attached keyboard will respond. The whole thing bricks whenever I send a large file on FTP. I am now completely lost as to the cause. Hardware, maybe?


NM. Found the problem. One of the hard drives just died, I think. *sigh* As I'm pretty sure they predate S.M.A.R.T. it's hard to know for sure, but the age alone makes it the likely cause.

<profanity>

Final Update:
Found the real cause. Thought it was hard drive from missing system files, fsck freaking out on boot etc. Turns out the RAM stick in slot 4 on the mobo was bad. Memtest found over 150 bad bytes in ten minutes. I guess the bad RAM was all in the upper part of the register or summat, and very large FTP transfers was the only thing I was doing to access the bad memory.

So. If anyone else ever has a machine randomly hardlock on large file transfers, start up memtest and go for a walk to cool down.