You can use PARSENAME :

SELECT *
FROM dbo.YourTable
WHERE PARSENAME(YourColumn,4) = '50'

Use Left and Charindex String function. Try this.

select * from table_1 where
left(Column_1,charindex('.',Column_1)-1) in('50','41','107')

This query will make sure that you're only capturing IP addresses with only 4 octets.

All octets will need to be in the specified range (currently set to 0-255 but can be changed in the where clause) you can also change the BETWEEN a AND b to IN (a, b, ...) and it will only capture those specific numbers.

It also returns the octets in their own columns as integers which would be a good way to store them moving forward in case you ever needed to do analysis on a specific range, then you won't need to parse text in the future.

Note: Because of the use of TRY_CAST this will only work on SQL Server 2012 and

WITH Octet_Position (column_1, position_1, position_2, position_3)
AS
(
    SELECT
        column_1,
        CHARINDEX('.', column_1),
        CHARINDEX('.', column_1, CHARINDEX('.', column_1) + 1),
        CHARINDEX('.', column_1, (CHARINDEX('.', column_1, CHARINDEX('.', column_1) + 1)) + 1)
    FROM Table_1
)
SELECT
    column_1 AS ip_address,
    TRY_CAST(SUBSTRING(column_1, 0, position_1) AS INT) AS octet_1,
    TRY_CAST(SUBSTRING(column_1, position_1 + 1, position_2 - position_1 - 1) AS INT) AS octet_2,
    TRY_CAST(SUBSTRING(column_1, position_2 + 1, position_3 - position_2 -  1) AS INT) AS octet_3,
    TRY_CAST(SUBSTRING(column_1, position_3 + 1, LEN(column_1) - position_3) AS INT) AS octet_4
FROM Octet_Position
WHERE
    --make sure there are three .'s
    position_1 > 0 AND
    position_2 > 0 AND
    position_3 > 0 AND

    --Make sure the octets are numbers
    TRY_CAST(NULLIF(SUBSTRING(column_1, 0, position_1), '') AS INT) IS NOT NULL AND
    TRY_CAST(NULLIF(SUBSTRING(column_1, position_1 + 1, position_2 - position_1 - 1), '') AS INT) IS NOT NULL AND
    TRY_CAST(NULLIF(SUBSTRING(column_1, position_2 + 1, position_3 - position_2 -  1), '') AS INT) IS NOT NULL AND
    TRY_CAST(NULLIF(SUBSTRING(column_1, position_3 + 1, LEN(column_1) - position_3), '') AS INT) IS NOT NULL AND

    --make sure the octects are in the correct range
    TRY_CAST(NULLIF(SUBSTRING(column_1, 0, position_1), '') AS INT) BETWEEN 0 AND 255 AND
    TRY_CAST(NULLIF(SUBSTRING(column_1, position_1 + 1, position_2 - position_1 - 1), '') AS INT) BETWEEN 0 AND 255 AND
    TRY_CAST(NULLIF(SUBSTRING(column_1, position_2 + 1, position_3 - position_2 -  1), '') AS INT) BETWEEN 0 AND 255 AND
    TRY_CAST(NULLIF(SUBSTRING(column_1, position_3 + 1, LEN(column_1) - position_3), '') AS INT) BETWEEN 0 AND 255

--declare @ip nvarchar(15) = '1.2.3.4'
--declare @ip nvarchar(15) = '333.2.3.4'
declare @ip nvarchar(15) = '50.2.3.4'

select @ip, 
       iif (   ( patindex('[0-9]%.[0-9]%.[0-9]%.[0-9]%', @ip) = 0)
            or ( patindex('%[^0-9.]%', @ip) > 0 )
            or ( len(@ip) - len(replace(@ip, '.', '')) <> 3 )
            or ( parsename(@ip, 4) not between 0 and 255 )
            or ( parsename(@ip, 3) not between 0 and 255 )
            or ( parsename(@ip, 2) not between 0 and 255 )
            or ( parsename(@ip, 1) <> 50 )
           , 'bad'
           , 'ok'
         )