Matching IP scopes.

Collapse
This topic is closed.
X
X
Collapse
 
  • Page of 1
  • Time
  • Show
Clear All
new posts
Previous template Next
  • Sandman
    #1

    Matching IP scopes.

    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]
    Tags: None
    • Oli Filth
      #2
      Re: Matching IP scopes.

      Sandman said the following on 27/02/2006 19:59:[color=blue]
      > 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?[/color]

      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

        Comment

        • Oli Filth
          #3
          Re: Matching IP scopes.

          Oli Filth said the following on 27/02/2006 20:05:
          [color=blue]
          > An IP address matches a given network IP address if:
          >
          > (Address ^ Mask) == (NetAddress ^ Mask)
          >[/color]

          Oops, those should be &, not ^...

          --
          Oli

            Comment

            • Sandman
              #4
              Re: Matching IP scopes.

              In article <mYIMf.60881$mf 2.26167@newsfe6-win.ntli.net>,
              Oli Filth <catch@olifilth .co.uk> wrote:
              [color=blue]
              > Sandman said the following on 27/02/2006 19:59:[color=green]
              > > 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?[/color]
              >
              > 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.[/color]

              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]

                Comment

                • Oli Filth
                  #5
                  Re: Matching IP scopes.

                  Sandman said the following on 27/02/2006 20:27:[color=blue]
                  > In article <mYIMf.60881$mf 2.26167@newsfe6-win.ntli.net>,
                  > Oli Filth <catch@olifilth .co.uk> wrote:
                  >[color=green]
                  >> Sandman said the following on 27/02/2006 19:59:[color=darkred]
                  >>> 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?[/color]
                  >> 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.[/color]
                  >
                  > 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?
                  >[/color]

                  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

                    Comment

                    • Andy Hassall
                      #6
                      Re: Matching IP scopes.

                      On Mon, 27 Feb 2006 21:27:43 +0100, Sandman <mr@sandman.net > wrote:
                      [color=blue]
                      >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?[/color]

                      The user-contributed notes on http://uk.php.net/ip2long may interest you.

                      --
                      Andy Hassall :: andy@andyh.co.u k :: http://www.andyh.co.uk
                      http://www.andyhsoftware.co.uk/space :: disk and FTP usage analysis tool

                        Comment

                        • Sandman
                          #7
                          Re: Matching IP scopes.

                          In article <BuJMf.19835$bw 1.4310@newsfe2-win.ntli.net>,
                          Oli Filth <catch@olifilth .co.uk> wrote:
                          [color=blue]
                          > Sandman said the following on 27/02/2006 20:27:[color=green]
                          > > In article <mYIMf.60881$mf 2.26167@newsfe6-win.ntli.net>,
                          > > Oli Filth <catch@olifilth .co.uk> wrote:
                          > >[color=darkred]
                          > >> 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.[/color]
                          > >
                          > > 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?
                          > >[/color]
                          >
                          > 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)[/color]

                          I get it now, I think I have it working. Thanks!


                          --
                          Sandman[.net]

                            Comment

                            Previous template Next
                            Working...