Bad performance & reliability with linux router. Why? =(
Up to yesterday my linux box was directly connected to the internet via a DSL connection. Now I got my hands onto a Pentium MMX 200 with 128MB ram which I wanted to turn into a firewall and eventually into a proxy/mail/dns/etc. server.
I now have it connect to the internet and masquerade to the internal lan. Also I have a firewall running on it and adjusted the one on my client box accordingly. However I noticed massive loss in reliability and performance and I don't know what is going wrong.
1) The router forwards incoming connections on two ports (one tcp and one udp) in order to get xmule running correctly on my client. This seems to work as I can connect to many servers quickly and I do get high IDs (which indicates that the port forwarding works correctly). But when I connected without the router my average download rates were about 40-90kb/sec, now I get only 0-5kb/sec and I left it running the whole night and on different servers. I don't see the router blocking any connections on the ports that I need so I don't know why this happens.
2) Another problem is with ftp. I wanted to download about 800mb of updates from an ftp server over night but the connection kept dropping after 15-30 mins. Even when I tried different servers. I don't have a clue either why this happens. (ports 20 and 21 are being accepted)
3) My third problem is that I can connect to almost any website without a problem. Only some sites like google.com and gmx.net do not work, I don't seem to get any answer back from these sites. I only have this problem when I have the router in place. With a direct connection, I can connect to these.
I would appreciate any hints or explanation as I think I made some mistake with the configuration but I can't seem to find it.
I can post both firewall scripts if you need more information but I didn't yet because they are generated by fwbuilder (lame, I know...) and are thus quite spammy.