So I had 4 Dedicated with 2 connection line. Each server had: > eth0, onboard with private IP (10.10.x.x) > eth1, LAN card with 2 public IP > Ubuntu 12.04.3 LTS Recently, I had to restart server1 and server4. And after that, I can't SSH nor ping server1 and server4. After trying to disable eth0 in /etc/network/interfaces and reboot again, I can connect and login to SSH. Now I had no idea why this would be happen. Right now server1 and server4 are running without eth0 enabled. Any help how to enable eth0 again without any problem to eth1? ps: English is not my native language.