I had a company computer(ubuntu 12.04LTS) taken home. My home use DSL and my company use LAN to connect to internet. The computer works well in my company, but I have to config it after taken home. I used pppoeconf to config the DSL successfully at home. and use pon dsl-provider to connect to internet. But after I take the computer back to company, I had to change back to LAN. After Google it, I modified the file /etc/network/interfaces
auto lo iface lo inet loopback auto dsl-provider iface dsl-provider inet ppp pre-up /sbin/ifconfig eth0 up # line maintained by pppoeconf provider dsl-provider auto eth0 iface eth0 inet manual
auto lo iface lo inet loopback #auto dsl-provider #iface dsl-provider inet ppp #pre-up /sbin/ifconfig eth0 up # line maintained by pppoeconf #provider dsl-provider #auto eth0 #iface eth0 inet manual
but this does not work: When reboot the computer, the network-manager shows wired network already connected, but not show the "Wired connection 1". ifconfig shows eth0 have ip address 192.168.1.108, but cannot connect to internet. I tried to add Wired Connection 1 manually, choose the MAC of eth0 in Device MAC address, and save. It shows: Connection add failed , Connecttion not visible or not available. (I thought it should work here. DHCP/Manual ip addresses both works well several day before.)
I had several other tries: I changed the /etc/network/interfaces file to
auto lo iface lo inet loopback #auto dsl-provider #iface dsl-provider inet ppp #pre-up /sbin/ifconfig eth0 up # line maintained by pppoeconf #provider dsl-provider auto eth0 iface eth0 inet manual
still not work. and changed to some static ip address not work, either. I think that pppoeconf make some change to the network-manager configuration or networking config, so that after stopped pppd, the network-manager does not work. Please give me some advices, thanks!