SQL Server 2017

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create table t( ip varchar(40) not null, mask varchar(40) not null);
insert into t(ip, mask) values ('10.0.1.38', '255.255.255.224')
1 rows affected

WITH CTE AS (
SELECT ip, mask, B.ipn, M.masknc
from t AS A 
CROSS APPLY ( 
SELECT (([1] * 256 + [2]) * 256 + [3]) * 256 + [4] AS ipn FROM
(SELECT CAST([value] AS BIGINT) AS value, ID = ROW_NUMBER() OVER(ORDER BY(SELECT NULL)) 
FROM STRING_SPLIT(A.ip, '.') ) AS src
PIVOT
(MAX(value) FOR ID in ([1],[2],[3],[4]) ) AS P ) AS B
CROSS APPLY ( 
SELECT CAST(256 AS BIGINT) * 256 * 256 * 256 - ((([1] * 256 + [2]) * 256 + [3]) * 256 + [4]) AS masknc FROM
(SELECT CAST([value] AS BIGINT) AS value, ID = ROW_NUMBER() OVER(ORDER BY(SELECT NULL)) 
FROM STRING_SPLIT(A.mask, '.') ) AS src
PIVOT
(MAX(value) FOR ID in ([1],[2],[3],[4]) ) AS P ) AS M
), CTE1 AS (
SELECT C.ip, C.mask, CAST(C.ipn / C.masknc AS BIGINT) * C.masknc AS netipn, 
32 - LOG(C.masknc, 2) AS maskc, 
E32 = CAST(256 AS BIGINT) * 256 * 256 * 256, 
E24 = CAST(256 AS BIGINT) * 256 * 256, 
E16 = CAST(256 AS BIGINT) * 256,
E8 = CAST(256 AS BIGINT)
FROM CTE AS C
), CTE2 AS (
SELECT C.ip, C.mask, netip1 = FLOOR(netipn / E24), netip2 = FLOOR((netipn % E24)/ E16),
netip3 = FLOOR((netipn % E16) / E8), netip4 = FLOOR(netipn % E8), C.maskc
FROM CTE1 AS C
)
SELECT C.ip, C.mask, CAST(C.netip1 AS VARCHAR(3)) + '.' + CAST(C.netip2 AS VARCHAR(3)) + '.' +
CAST(C.netip3 AS VARCHAR(3)) + '.' + CAST(C.netip4 AS VARCHAR(3)) + '/' + CAST(C.maskc AS VARCHAR(4)) AS netip  
FROM CTE2 AS C


ip
mask
netip


10.0.1.38
255.255.255.224
10.0.1.32/27


SELECT CAST(256 AS BIGINT) *256*256*256, CAST(12.844 AS BIGINT)


(No column name)
(No column name)


4294967296
12