A slightly noob subnet mask question

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    • #7100
      Dranex
      Participant

      Hi guys, new forum member here!

      I’m currently studying like crazy with the hope of doing an OSCP qualification when I learn enough, but as my question was network related I thought it maybe best to post it here..

      I’ve been following this guide
      http://www.infiltrated.net/pentesting101.html

      and learning all the essential areas it describes until i get to the following line from the networking part..

      “You will need a firm grasp on subnetting. The differences between a Class A, B and C network, and no a Class C is not a slash twenty four (/24). If that came as a surprise to you, then you seriously need to go back and read. “

      This has confused me a LOT, from my previous University studies I was lead to believe that a Class C subnet IS slash 24 (/24) as it has 24 of the possible 32 bits active (255.255.255.0) and pretty much everything i’ve researched has backed that up.. have I missed something obvious here??

    • #44157
      l33t5h@rk
      Participant

      Perhaps they mean don’t just think that because something has a /24 that means it’s a Class C?

      Network classes & first octets (for classful networks)
      A 0 – 127
      B 128 – 191
      C 192 – 223

    • #44158
      Triban
      Participant

      Some elaboration on l33t5h@rk’s info…

      You can take a Class A/B network and subnet it down further to smaller networks.  for instance 10.0.0.0/24, the octets fall into a Class A network but the CIDR notation makes it look as if it is a Class C.  It may contain the same number IPs but it is part of a much larger network.

      Someone correct me if I am off, but that is how I interpret it.

    • #44159
      l33t5h@rk
      Participant

      @3xban wrote:

      You can take a Class A/B network and subnet it down further to smaller networks.  for instance 10.0.0.0/24, the octets fall into a Class A network but the CIDR notation makes it look as if it is a Class C. 

      What he said  😀

      This is the only way I can see the comments making sense is if it was served as a warning as opposed to a fact.

    • #44160
      lorddicranius
      Participant

      Exactly what l33t5h@rk and 3xban have said.  Cisco has a good tutorial on subnetting:

      http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800a67f5.shtml

      As well as Wikipedia’s page on subnetting:

      http://en.wikipedia.org/wiki/Subnetwork

    • #44161
      KrisTeason
      Participant

      Hi Dranex,

      Welcome to EthicalHacker.net ! Just incase this helps, I’ve compiled a decent size list of video links that’ll should bring you up to par on Subnetting.

      Subnetting in 6 Easy Steps Part 1
      http://www.youtube.com/watch?v=wl5_J0UtINg

      Subnetting in 6 Easy Steps Part 2
      http://www.youtube.com/watch?v=vi1dtaQ1FEo

      Subnetting in 6 Easy Steps Part 3
      http://www.youtube.com/watch?v=F68dgzY652k

      I’ve uploaded the bottom two that were taken directly from a college class I took called TCP/IP Protocols.

      Subnetting Secrets – 26 Bit Mask Example
      http://www.youtube.com/watch?v=A9Ica4EfDU8

      Subnetting Example
      http://www.youtube.com/watch?v=93F1Vbc2ya8

    • #44162
      Dranex
      Participant

      Overwhelmed by the help guys, really appreciated.

    • #44163
      El33tsamurai
      Participant

      Are you planning on taking the OSCP soon?

    • #44164
      Dranex
      Participant

      I would love to, but i’m a few months of learning away I think, I would love to learn python first too, but i’m not sure exactly how essential that would be..

    • #44165
      Dranex
      Participant

      Exactly what point do I need to be at before I should be comfortable taking it on with the course materials and research supplementing?

      I studied Computing in Uni (Forensics unfortunately, wishing I went down the security route to begin with) so my knowledge of computing is pretty high, most of the stuff we did was with Windows but from a personal geekage point of view I understand Backtrack Linux pretty well now.

      I understand networking and the layouts, the OSI model, TCP/IP, Subnetting (thanks to the help you guys left me). I learnt Vivek’s Metasploit Megaprimer about a thousand times and read the pentesting with Metasploit book, so i’m pretty comfortable with msf now too.

      Is an exploit friendly language the next step or is there somewhere I could better spend my time such as specific exploits, SSH tunneling, SQL injections?

      Any help you can give is always greatly appreciated.

      (p.s. If you think this question is better off moved to the OSCP specific section I understand)

    • #44166
      Triban
      Participant

      I was trying to look for the thread were someone put together a very simple list of things you should know before hitting the test but I couldn’t find it.  But luckily I jotted it down for my own reference:

      Learn Python Scripting (diveintopython.org) – I have also been using learnpythonthehardware.org

      BASH Scripting

      Know what assembly language looks like (book – Hacking: the art of exploitation by John Erickson)

      Organizational skills for all the data you will enumerate

      A joy of puzzles

      Whoever wrote that please chime in. 

    • #44167
      rattis
      Participant

      I know johy come late, but the thing to remember

      Classful networking. Class A, B, C, D and E (if I remember them correctly)

      CIDR (Classless Inner Domain Routing) you’re slashes and subnets. (if I remember correctly) 🙂

      Back in the 90s, I worked for one of the original six backbone providers. I remember it took two of us, to explain to an ISP the concept of CIDR. They were used to classes, not the classless.

    • #44168
      eth3real
      Participant

      @3xban wrote:

      learnpythonthehardware.org

      Should this be learnpythonthehardway.org?

      I haven’t used either of those sites, but I’m going to have to give them a shot. 🙂

    • #44169
      Triban
      Participant

      woops  yeah way not ware 😀

    • #44170
      El33tsamurai
      Participant

      @Dranex wrote:

      I would love to, but i’m a few months of learning away I think, I would love to learn python first too, but i’m not sure exactly how essential that would be..

      I am taking the class right now and I would say basic python skills are needed.

      http://code.google.com/intl/ru/edu/languages/google-python-class/

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