I connected to a new network 2 days ago and I have the same problem as you.
That's an old problem, I already had it before with the same wireless network.
I'm running debian unstable so it could be the same.
You're not talking of wireless so it look like a conflict somewhere.
For me it works 1 time out of 20. I've never rebooted tho', can't be bothered.
I will look at this because it's annoying.
Meanwhile, I do the dhcp myself:
ifconfig eth2 192.168.1.20 up <--- set it to static .20
route add default gw 192.168.1.1 <--- that's the gateway to go outside
modify /etc/resolv.conf and add
nameserver 192.168.1.1 <--- dns server
in other situations i have network after boot but after a few minutes the network is off again.
You mean sometimes you get disconnected?
This I don't have and that's far worse!
Try static and see if it stays longer
If anybody has idea on this, I'm interested too