I have a server running Debian stable, which functions as a router/firewall and mailserver. It has two NICs, both realtek 8139. eth0 is connected to my LAN and has ip 192.168.0.1. eth1 is connected to my ADSL ethernet modem and has ip 18.104.22.168 which it gets through DHCP and is dynamic.
I used to have the same setup on another server where it functioned perfectly. That server had basically the same hardware but used a 3com ISA NIC for eth1.
Since I'm using this new server, which is a little bit faster, the internet connection sometimes fails on me. First I thought it might have something to do with the DHCP, because I sometimes noticed I had no valid leases. This is not the case however, since the lack of valid leases is due to the fact that the internet connection fails.
I suspect it has something to do with the whole network, because when I have a SSH connection in my internal network (thus to eth0) opened, this connection failes too. The eth0 revives though, since I can open a new SSH connection immediately after.
I have found that running /etc/init.d/networking restart brings the network back up. Also when I run and close tcpdump the connection is back to life.
Does anyone have any idea what might be going on here? It totally beats me, and if I don't cure this very soon my housemates might beat me too for their internet not working properly
Any help would be greatly appreciated!