eth0 not working after rebooting

[bone2006]

I'm not sure what's going on, but I have two computers that both aren't working after I reboot them. When I boot up the machine and do ifconfig, eth0 is missing.

If I issue $sudo ifup eth0 then the ethernet is working, but I'm not sure why I'm booting up without a connection. Even after $sudo ifup eth0
The networking app that's in the taskbar is missing.

looked at dmesg and it looks normal
$dmesg | grep -i eth

my interfaces file
iface eth0 inet static
address 192.168.15.146
netmask 255.255.255.0
gateway 192.168.15.1

Any help is appreciated it.

[Iowan]

Add "auto eth0" to /etc/network/interfaces, then reboot/restart networking.

I presume the two lines defining "lo" are still in /etc/network/interfaces as well...
So /etc/network/interfaces should look like:

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
address 192.168.15.146
netmask 255.255.255.0
gateway 192.168.15.1

[bone2006]

No, I didn't have either the auto lo nor the auto eth0 in my interfaces, but I'll give that a try.
I've been using the same interfaces configuration for years though.

Thought lo was just a loopback and isn't necessary one way or another. But eitherway I'll make that changes now and see if that works for me.

appreciate the help