Note in the previous second configuration, the NAT pool “ovrld”only has a range of one address. The keyword overload used in the ip nat inside source list 7 pool ovrld overload command allows NAT to translate multiple inside devices to the single address in the pool.Reference: http://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a0080094e77.shtml