Linux Command line Connection Network __linux

For a long time or at the command line using Ifconfig to connect to the network, can only be temporarily replaced by Ifup.

I use ifconfig eth0 down after the first Nic down, in the upper right corner of the connection icon a fork, which means that the network is disabled, but when I use ifconfig eth0 IP netmask Broadcast command configured network IP is still not good, with ifconfig eth0 up after still not, there is no way can only be automatically obtained by the Ifup IP.

Hope that after a period of time to make up, simple network configuration is still needed.

PS. I want to ifconfig fixed IP, but not on the network, can only use the ifup automatically get IP.