The value of the object tmnxLocUsrDbDhcpMaskPreNum specifies
the number of characters to remove from the start of the incoming
string before it is matched against the value configured in the
corresponding object in the tmnxLocUsrDbDhcpTable.
At least one of the values of tmnxLocUsrDbDhcpMaskPreNum and
tmnxLocUsrDbDhcpMaskPreStr must be equal to the default value.