VBA

Sub SubnetFinder()
    ' Dichiarazione variabili
    Dim i, j As Integer
    Dim subnetstart(), matchedmask, subnetlength() As Variant
    Dim sourceip(), sourceipoct1(), sourceipoct2(), sourceipoct3(), sourceipoct4() As Variant
    Dim subnetstartoct1(), subnetstartoct2(), subnetstartoct3(), subnetstartoct4()  As Variant
    Dim subnetendoct1(), subnetendoct2(), subnetendoct3(), subnetendoct4() As Variant
    Dim matchedsubnet(), matchedsubnetoct1(), matchedsubnetoct2(), matchedsubnetoct3(), matchedsubnetoct4() As Variant
    
    ' Inizializzazione variabili
    subnetstart = Sheets("Sheet1").Range("H3:H4").Value
    subnetstartoct1 = Sheets("Sheet1").Range("J3:J4").Value
    subnetstartoct2 = Sheets("Sheet1").Range("K3:K4").Value
    subnetstartoct3 = Sheets("Sheet1").Range("L3:L4").Value
    subnetstartoct4 = Sheets("Sheet1").Range("M3:M4").Value
    
    subnetendoct1 = Sheets("Sheet1").Range("N3:N4").Value
    subnetendoct2 = Sheets("Sheet1").Range("O3:O4").Value
    subnetendoct3 = Sheets("Sheet1").Range("P3:P4").Value
    subnetendoct4 = Sheets("Sheet1").Range("Q3:Q4").Value
    
    sourceip = Sheets("Sheet1").Range("B3:B4").Value
    sourceipoct1 = Sheets("Sheet1").Range("C3:C4").Value
    sourceipoct2 = Sheets("Sheet1").Range("D3:D4").Value
    sourceipoct3 = Sheets("Sheet1").Range("E3:E4").Value
    sourceipoct4 = Sheets("Sheet1").Range("F3:F4").Value

    matchedsubnetoct1 = Sheets("Sheet1").Range("S3:S4").Value
    matchedsubnetoct2 = Sheets("Sheet1").Range("T3:T4").Value
    matchedsubnetoct3 = Sheets("Sheet1").Range("U3:U4").Value
    matchedsubnetoct4 = Sheets("Sheet1").Range("V3:V4").Value
    
    matchedmask = Sheets("Sheet1").Range("I3:I4").Value


    'Iterazione
    For j = 1 To 2
        For i = 1 To 2
              
            If ((sourceipoct1(j, 1) = subnetstartoct1(i, 1)) And (sourceipoct1(j, 1) <= subnetendoct1(i, 1))) Then
                matchedsubnetoct1(j, 1) = subnetstartoct1(i, 1)
                
                If ((sourceipoct2(j, 1) >= subnetstartoct2(i, 1)) And (sourceipoct2(j, 1) <= subnetendoct2(i, 1))) Then
                    matchedsubnetoct2(j, 1) = subnetstartoct2(i, 1)
                
                    If ((sourceipoct3(j, 1) >= subnetstartoct3(i, 1)) And (sourceipoct3(j, 1) <= subnetendoct3(i, 1))) Then
                        matchedsubnetoct3(j, 1) = subnetstartoct3(i, 1)
                    
                        If ((sourceipoct4(j, 1) >= subnetstartoct4(i, 1)) And (sourceipoct4(j, 1) <= subnetendoct4(i, 1))) Then
                            matchedsubnetoct4(j, 1) = subnetstartoct4(i, 1)
                               
                            Worksheets("Sheet1").Cells(j + 2, 19) = matchedsubnetoct1(j, 1)
                            Worksheets("Sheet1").Cells(j + 2, 20) = matchedsubnetoct2(j, 1)
                            Worksheets("Sheet1").Cells(j + 2, 21) = matchedsubnetoct3(j, 1)
                            Worksheets("Sheet1").Cells(j + 2, 22) = matchedsubnetoct4(j, 1)
                            Worksheets("Sheet1").Cells(j + 2, 23) = matchedmask(i, 1)
                        End If
                    End If
                End If
            End If
        Next i
    Next j
End Sub