Strange network problem

it290 · n00b Joined: 29 Jul 2002 Posts: 22

Hello all,

I've been having a weird network problem for the last few days, and I'm not sure what could be causing it. Basically what happens is that when I start a program that uses any type of direct connection, it blocks other programs from working. So for example, if I start up an ftp client, I am able to connect to the server fine, but afterwards my irc client, gaim, etc are not able to connect to their respective servers. Likewise, if I start up xchat first, it works fine but I am not able to connect via ftp. Rebooting fixes the problem, but restarting eth0 does not. I have a fairly basic networking setup -- I'm behind a DSL modem/router which is set up to forward all incoming connections to my Gentoo machine. I am also running a fairly basic set of services -- apache2, sshd, and postfix basically. This just started happening in the last couple days, and I haven't made any changes that I think would case this. My IP address has also not changed. I'd post more information, but I'm not sure what would be relevant. Has anyone encountered something like this before?

edit -- I should also add that even after the first connection, browsing the web and mail still work fine, for example. I can send mail and postfix will get it out, and I can see my webserver from another machine, even one that's located on a different network. Also, I just noticed that after the initial connection, other machines on my network are likewise unable to initiate connections -- ie if I use xchat on my linux machine, my Mac won't be able to FTP. This leads me to believe it's a router problem, but rebooting the Linux box cures it (at least for the first connection). Weird, eh?

Darknight · Guru Joined: 26 Jan 2004 Posts: 485 Location: Italy

Some "limit" statement in your iptables rules?
It's just the first thing that comes to my mind.

it290 · n00b Joined: 29 Jul 2002 Posts: 22

No, I wish it were something like that, but the problem is still happening even after turning off all filtering on my box and on the router (except for basic NAT translations). Could it be something upstream?

Darknight · Guru Joined: 26 Jan 2004 Posts: 485 Location: Italy

If there's some firewall you don't have access to, yes, it could be.
But I fail to imagine what could cause this problem, it's ridiculous, seems like you can only open one connection at a time...
Maybe like a lock on the network interface, so that an application gets exclusive access to it...