Check IP Range

Hi,

I need to implement a mechanism that will check after login successfull, if the user IP address is within a given range!

For example this range: 194.28.12.1 to 194.28.12.20

I need to check if the current ip address of the user that just loged (for example: 194.28.12.50) is within that range or not?

Thanks!

Re: Check IP Range

I know this is not related to your question, but as a network engineer I feel it would be wrong not to mention this.

You are aware that 194.x.x.x is not a private ip address range?

Your reserved private ip address ranges are:

RFC1918 name	IP address range	number of addresses per network	classful description	largest CIDR block (subnet mask)	host id size
24-bit block	10.0.0.0 10.255.255.255	16,777,214	single class A	10.0.0.0/8 (255.0.0.0)	24 bits
20-bit block	172.16.0.0 172.31.255.255	65,534	16 contiguous class Bs	172.16.0.0/12 (255.240.0.0)	20 bits
16-bit block	192.168.0.0 192.168.255.255	254	256 contiguous class Cs	192.168.0.0/16 (255.255.0.0)	16 bits

I know this is not your question, but I just felt I needed to point that out. You can run into serious problems reaching public ip addresses if you're using them for internal networking.

Re: Check IP Range

Hi,

Yes I am aware of that ... was just the first example that passed through my head at that time and I do have some network knowledge :) Was just an example (bad one) :)

Re: Check IP Range

Ok good deal. I just wanted to make sure you were aware.

As to getting the ip address of the client connecting you should be able to retrieve their IP address like this:

Dim strIP as String = Request.UserHostAddress()

Once you have their IP address in a string you could preform a split on the IP on "." to get an array and then compare each array value to see if it meets your criteria.

So given your criteria above I could this:

Dim ipArray as Array = Split(Request.UserHostAddress(), ".")

'Now Check to make sure each octet is in the correct range:

Dim ipCheck as Boolean = False

If ipArray(0) = 194 and ipArray(1) = 28 and ipArray(2) = 12 and (ipArray(3) > 0 and ipArray(3) < 21) Then

ipCheck = True

End If

Our boolean assumes the host is invalid and only will return as true if all criteria is met.

Does that help?

Re: Check IP Range

This will return false for your IP when you run it from Visual Studio because it's going to see your ip as the local loopback address 127.0.0.1.

If you upload this to your server and run it from a client you'll see different results when it's not grabbing your loopback address:

<%@ Page Language="VB" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<script runat="server">
        
    Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
        Dim strIP As String = Request.UserHostAddress()
        Response.Write(strIP & ": ")
        Response.Write(checkIP(strIP) & "<br />")
        Response.Write("194.12.28.1: ")
        Response.Write(checkIP("194.28.12.1") & "<br />")
    End Sub
        
    Function checkIP(ByVal ip1 As String) As Boolean
        Dim ipCheck As Boolean = False
        Dim ipArray As Array = Split(ip1, ".")
        If ipArray(0) = 194 And ipArray(1) = 28 And ipArray(2) = 12 And (ipArray(3) > 0 And ipArray(3) < 21) Then
            ipCheck = True
        End If
        Return ipCheck
    End Function
</script>

<html xmlns="http://www.w3.org/1999/xhtml">

<head runat="server">
<title></title>
</head>

<body>
    <form id="form1" runat="server">
    <div>
    </div>
    </form>
</body>
</html>