Hello, I am using a debian (lenny) linux on small home router (no X server, ipv6 completely disabled, all network tweaks like tcp_wmem are increased).

The router computer have two interfaces: one to the ISP and other to my home network (namely to wifi AP). I have pptp connection to ISP and using iptables NAT to share the internet to my home network. All is working fine except one thing.

The download speed (measured while downloading a large (700Mb) file) of the router box is about average 500Kb/s.

At the same time download speed from my notebook (fedora linux, as well as other different Windows notebooks I've tried), connected to the internet through this router (!) and downloading the same file is almost 1.4Mb/s (that is actually a limit of my ISP connection).

When I run these tests I am sure, I have no other tcp connections active, I can tell this by netstat output. I have no caching (or any other) proxies either.

Moreover when i start torrents (rtorrent), the download speed falls down dramatically to 50-150 Kb/s, while actual torrent upload (with no downloading) speed is about 50 Kb/s. And still, my notebook download speed is about 1.3-1.4Mb/s.

As I mentioned, I have ipv6 disabled, no X server running, no proxies.

I am trying to do something with this for almost a week, and many time I have already wasted on this problem. When I used different ISP with the same environment, there were no problems. Unfortunately, I can not fallback to the previous ISP. Actually I even don't want to, because all clients behind this router work fine, so it seems to be a problem in a debian box itself.

I have absolutely no idea left on what can cause this problem. Nor even how to diagnose it.

It would be great if somebody told me at least HOW to find out where my problem can be.

There are too many config files to list here all of them, but I can do that on request.

Thanks in advance.