Before we start with code let us take a sample IP address, does 127.0.0.1 look familiar? Yes that is your local IP address.

Here it is in decimal and binary

127 0 0 1

01111111 00000000 00000000 00000001

Now to convert, you would take the first value,

add the second value + 256

add the third value + (256 * 256) = 65536

add the fourth value + (256 * 256 * 256) =16777216

So in our case the select would be

```
select
1 +
0 * 256 +
0 * 65536 +
127 * 16777216
```

which is

2130706433

So to convert from IP Adress to integer is very simple, you use PARSENAME to split it up and do the math. Here is the function.

```
CREATE FUNCTION dbo.IPAddressToInteger (@IP AS varchar(15))
RETURNS bigint
AS
BEGIN
RETURN (CONVERT(bigint, PARSENAME(@IP,1)) +
CONVERT(bigint, PARSENAME(@IP,2)) * 256 +
CONVERT(bigint, PARSENAME(@IP,3)) * 65536 +
CONVERT(bigint, PARSENAME(@IP,4)) * 16777216)
END
GO
```

But how do you get 127.0.0.1 out of 2130706433?

It is the reversed of what we did before (surprise) so instead of multiplying we will be dividing

Here is the funcion

```
CREATE FUNCTION dbo.IntegerToIPAddress (@IP AS bigint)
RETURNS varchar(15)
AS
BEGIN
DECLARE @Octet1 bigint
DECLARE @Octet2 tinyint
DECLARE @Octet3 tinyint
DECLARE @Octet4 tinyint
DECLARE @RestOfIP bigint
SET @Octet1 = @IP / 16777216
SET @RestOfIP = @IP - (@Octet1 * 16777216)
SET @Octet2 = @RestOfIP / 65536
SET @RestOfIP = @RestOfIP - (@Octet2 * 65536)
SET @Octet3 = @RestOfIP / 256
SET @Octet4 = @RestOfIP - (@Octet3 * 256)
RETURN(CONVERT(varchar, @Octet1) + '.' +
CONVERT(varchar, @Octet2) + '.' +
CONVERT(varchar, @Octet3) + '.' +
CONVERT(varchar, @Octet4))
END
```

Now let’s try this out, first run this

```
select dbo.IPAddressToInteger('127.0.0.1')
```

That returns 2130706433

Now run this

```
select dbo.IntegerToIPAddress(2130706433)
```

That returns 127.0.0.1

Thanks to K. Brian Kelley for the inspiration for this post, you can also check http://www.truthsolutions.com/ to see some of his books

And also check out the related Order IP Addresses wiki article which I wrote a while ago