First go to virtual Box, your VM ->Settings -> Network ->Advanced
Display the Advance options and click the refresh button for Mac Address, then click OK
Now start the VM and login.
Remove from HWADDR line from /etc/sysconfig/network-scripts/ifcfg-eth0
You should remove something like:
Change eth0 by eth1 from ifcfg-eth0
Now restart network:
#sudo /etc/init.d/network restart
ifconfig will show you now your new IP address
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