So, I have this list of valid IP scopes, in the form below. How do I
match if $_SERVER[REMOTE_ADDR] is covered in any of these scopes?
193.11.120.0/21
193.11.128.0/24
193.11.129.0/24
193.11.130.0/24
193.11.131.0/24
First, I don't really know how to interprete the "/24" ending. I am
guessing that "193.11.131.0/24" means "193.11.131.X to 193.11.131.Y"
or something, but what? When that's translated to something useful,
how do I match IP numbers reliably?
Anyone done this?
--
Sandman[.net]
6  1767 
Sandman said the following on 27/02/2006 19:59: So, I have this list of valid IP scopes, in the form below. How do I
match if $_SERVER[REMOTE_ADDR] is covered in any of these scopes?
193.11.120.0/21
193.11.128.0/24
193.11.129.0/24
193.11.130.0/24
193.11.131.0/24
First, I don't really know how to interprete the "/24" ending. I am
guessing that "193.11.131.0/24" means "193.11.131.X to 193.11.131.Y"
or something, but what? When that's translated to something useful,
how do I match IP numbers reliably?
The /XX represents the length of the subnet mask in bits, so your hunch
is pretty much correct.
An IP address matches a given network IP address if:
(Address ^ Mask) == (NetAddress ^ Mask)
where Mask = 11111...0000, the number of ones given by the /XX.
--
Oli
Oli Filth said the following on 27/02/2006 20:05: An IP address matches a given network IP address if:
(Address ^ Mask) == (NetAddress ^ Mask)
Oops, those should be &, not ^...
--
Oli
In article <mY*******************@newsfe6-win.ntli.net>,
Oli Filth <ca***@olifilth.co.uk> wrote: Sandman said the following on 27/02/2006 19:59: So, I have this list of valid IP scopes, in the form below. How do I
match if $_SERVER[REMOTE_ADDR] is covered in any of these scopes?
193.11.120.0/21
193.11.128.0/24
193.11.129.0/24
193.11.130.0/24
193.11.131.0/24
First, I don't really know how to interprete the "/24" ending. I am
guessing that "193.11.131.0/24" means "193.11.131.X to 193.11.131.Y"
or something, but what? When that's translated to something useful,
how do I match IP numbers reliably?
The /XX represents the length of the subnet mask in bits, so your hunch
is pretty much correct.
An IP address matches a given network IP address if:
(Address ^ Mask) == (NetAddress ^ Mask)
where Mask = 11111...0000, the number of ones given by the /XX.
Ok, but how do I calculate it? Bits you say, but how do I translate 24
bits to addresses? For instance, the first line above, what addresses
does it cover?
--
Sandman[.net]
Sandman said the following on 27/02/2006 20:27: In article <mY*******************@newsfe6-win.ntli.net>,
Oli Filth <ca***@olifilth.co.uk> wrote:
Sandman said the following on 27/02/2006 19:59: So, I have this list of valid IP scopes, in the form below. How do I
match if $_SERVER[REMOTE_ADDR] is covered in any of these scopes?
193.11.120.0/21
193.11.128.0/24
193.11.129.0/24
193.11.130.0/24
193.11.131.0/24
First, I don't really know how to interprete the "/24" ending. I am
guessing that "193.11.131.0/24" means "193.11.131.X to 193.11.131.Y"
or something, but what? When that's translated to something useful,
how do I match IP numbers reliably?
The /XX represents the length of the subnet mask in bits, so your hunch
is pretty much correct.
An IP address matches a given network IP address if:
(Address ^ Mask) == (NetAddress ^ Mask)
where Mask = 11111...0000, the number of ones given by the /XX.
Ok, but how do I calculate it? Bits you say, but how do I translate 24
bits to addresses? For instance, the first line above, what addresses
does it cover?
An IP address is a 32-bit quantity, which can be represented as A.B.C.D,
where the actual 32-bit value is given by:
Y = (A * 2^24) + (B * 2^16) + (C * 2^8) + D
[I'm using ^ to represent "to the power of" in this case.]
So convert your test address and network address to this form, either
directly or by using the ip2long() function.
Then form your subnet mask as a 32-bit value.
[HINT: (2^X - 1) = (1000....000 - 1) = 111....111]
Then test the equality of the expression I originally posted, noting
that I got it wrong, and it should be:
(Address & Mask) == (NetAddress & Mask)
--
Oli
In article <Bu******************@newsfe2-win.ntli.net>,
Oli Filth <ca***@olifilth.co.uk> wrote: Sandman said the following on 27/02/2006 20:27: In article <mY*******************@newsfe6-win.ntli.net>,
Oli Filth <ca***@olifilth.co.uk> wrote:
Sandman said the following on 27/02/2006 19:59:
So, I have this list of valid IP scopes, in the form below. How do I
match if $_SERVER[REMOTE_ADDR] is covered in any of these scopes?
193.11.120.0/21
193.11.128.0/24
193.11.129.0/24
193.11.130.0/24
193.11.131.0/24
First, I don't really know how to interprete the "/24" ending. I am
guessing that "193.11.131.0/24" means "193.11.131.X to 193.11.131.Y"
or something, but what? When that's translated to something useful,
how do I match IP numbers reliably?
The /XX represents the length of the subnet mask in bits, so your hunch
is pretty much correct.
An IP address matches a given network IP address if:
(Address ^ Mask) == (NetAddress ^ Mask)
where Mask = 11111...0000, the number of ones given by the /XX.
Ok, but how do I calculate it? Bits you say, but how do I translate 24
bits to addresses? For instance, the first line above, what addresses
does it cover?
An IP address is a 32-bit quantity, which can be represented as A.B.C.D,
where the actual 32-bit value is given by:
Y = (A * 2^24) + (B * 2^16) + (C * 2^8) + D
[I'm using ^ to represent "to the power of" in this case.]
So convert your test address and network address to this form, either
directly or by using the ip2long() function.
Then form your subnet mask as a 32-bit value.
[HINT: (2^X - 1) = (1000....000 - 1) = 111....111]
Then test the equality of the expression I originally posted, noting
that I got it wrong, and it should be:
(Address & Mask) == (NetAddress & Mask)
I get it now, I think I have it working. Thanks!
--
Sandman[.net] This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics
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