/etc/network/interfaces
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auto lo # auto enable lo
iface lo inet loopback # lo is an inet(mean ipv4) interface used as lookback
iface eth0 inet dhcp # eth0 is an inet interface use dhcp to configure it
address a.b.c.d #-------------------
netmask 255.255.255.0 # should these be dynamic ?
gateway a.b.c.1 #-------------------
auto eth0 # auto enable eth0
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# command to execute, restart networking service
/etc/init.d/networking restart