Why do you need to reenter the IP? Since it is different each time you reboot? It means the IP is dynamic one - you need the dhclient or dhcpc run with reboot process.
If the each time the IP you reenter is the same one - your eth static settings are wrong.
Anyway investigate /etc/sysconfig/network-scripts/ifcfg-eth0 file. It keeps the network settings. And allows to define the IPs or dhcp client usage necessity.
|