NAT problem with ADSL? No!

Ha! Finally I found a solution for the problem that was irritating me and my friends at home. First, let me explain what’s in our home:

We have an ADSL connection, with the ADSL modem in bridge mode. Then we have a little server (K6-II 300, 128MB RAM) running only the base system. The server has to network nics: a wireless one and a normal. The normal NIC is with the modem, and the wireless NIC serves our hungry-for-net notebooks. Then the server shares the ADSL connection with iptables and NAT. Simple, huh?

The Problem

So this is the problem: some sites did not show up or function, CVS was always broken… This was really weird because everything was normal, there was not a good reason to only a few sites not work. I got a workaround for us: use an external proxy of mine to access the sites, and it worked for months! Some days ago, we were angry about this issue and I thought. I thought. I thought, and while I was in bed, I had an idea to check the network status of the NICs.

Then I finally discovered the problem!

Whaaa? What is this? ppp0’s MTU is 1492? Right! ADSL ppp conections are always with MTU 1492!

Why our NIC isn’t? Let me try this…


server-# ifconfig wlan0 mtu 1492
client-# ifconfig wlan0 mtu 1492


Hey! Everything is working now! MTU was killing us! I hope this will help some people that have this problem 😉