I'm running Ubuntu 10.04 and eht0 was setup in installation as dhcp, which is good because I'm running this as my WAN connection for a router.

When I add eth1 to the interfaces file I set it to static with IP address 192.168.1.2 (Linksys router/gateway is 192.168.1.1) here is what I enter:
auto eth1
iface eth1 inet static
address 192.168.1.2
network 192.168.1.0
netmask 255.255.255.0
broadcast 192.168.1.255
gateway 192.168.1.1

I then restart the network (/etc/init.d/networking restart) and from then on I can't get an internet connection. I go back into the interfaces file and comment out the entire entry of eth1 with "#"'s, save, restart network but it still hangs on any network command. I then set the interfaces file to it's original setup, restart services and nothing. I have to reboot the computer to get it to work. This doesn't make sense to me.

I don't know if this matters but I'm using a PCI-Express dual port NIC but I believe the same thing happens with the two on-board NIC's as well.

Any ideas about why this is happening? BTW, there aren't any other computers with the ip address 192.168.1.2 either.

Hello,

Have a look at the udev rules file /etc/udev/rules.d/70-persistent-net.rules if that changes by any chance. Ubuntu (and other distros too for that matter but not all) can behave pretty strange with udev when you manually start editing files without taking into account the udev rule set.

Kind regards,

Eric

I remember seeing reports that '/etc/init.d/networking restart' might not work as expected. In my particular case it failed to bring back up an interface. Try using ifup ifdown, or reboot the machine if you can. Your settings for eth1 look fine.