I'm not sure which report that is (I don't have it) but this should work/give you the solution, you just put in whatever the IP address field the report uses in there:
Order By Cast(ParseName(tblAssets.IPAddress, 4) As INT),
Cast(ParseName(tblAssets.IPAddress, 3) As INT),
Cast(ParseName(tblAssets.IPAddress, 2) As INT),
Cast(ParseName(tblAssets.IPAddress, 1) As INT)