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Subnet class

Discussion in 'Networks' started by Raffaz, Dec 30, 2006.

  1. Raffaz

    Raffaz Kebab Lover Gold Member

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    I was talking to one of my mates about the different classes for IPs and subnet masks. I thought that they only worked with the same class, like class A to class A, but he says thats wrong. Something to do with subnetting and not subnetting. Can anyone explain this to me? Cheers

    Mick
     
    Certifications: A+, MCP, MCDST, AutoCAD
    WIP: Rennovating my house
  2. AJ

    AJ Administrator Administrator

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    Hi Mick

    WIKI is your friend :D
     
    Certifications: MCSE, MCSA (messaging), ITIL Foundation v3
    WIP: Looking at doing ..................
  3. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    You need to realize that there is classfull addresing, and classless addressing. They work quite differently.

    Classfull is the old way, but still appears in exams because there are still real world examples being used. This uses the Class A,B and C system depending on the number of bytes in the network address. In addition, the classes are confined to specific ranges of the first byte. Classfull addressing has subnetting where the network address range issued can be split into smaller chunks.

    Classless is the way the Internet works now, and the division between the network address and the host address can be anywhere in the bitstring, not just at byte boundaries. In this scheme the value of the first byte doesn't determing anything about the length of the mask, so the mask has to be specified. Subnetting is merely taking a range and using a larger mask size for portions of that range.

    Your question is worded so vaguely :biggrin that it is difficult to know quite what is being said.

    I would recomend a read of this section of the excellent TCP/IP Guide.

    Harry.
     
    Certifications: ECDL A+ Network+ i-Net+
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  4. Boycie
    Honorary Member

    Boycie Senior Beer Tester

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    Mick,

    If you have a *standard* classfull mask, you know there is no subnetting involved;

    255.0.0.0
    255.255.0.0
    255.255.255.0

    Another good online guide need IE 6 (I haven't tested it on 7).

    Si
     
    Certifications: MCSA 2003, MCDST, A+, N+, CTT+, MCT
  5. Bluerinse
    Honorary Member

    Bluerinse Exabyte Poster

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    Mick, what do you mean by *worked with the same class*?

    A node with a class A IP address can communicate with nodes on a class B or C network id but they need a *router* between the networks. The routers job is to route packets to and from the different networks.

    This is a very complex topic and my post is an oversimplification but it might help :rolleyes:
     
    Certifications: C&G Electronics - MCSA (W2K) MCSE (W2K)
  6. Boycie
    Honorary Member

    Boycie Senior Beer Tester

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    Mick,

    Perhaps you are confused by the fact that without a router, different subnets will not communicate?

    If you had ten XP machines in your front room plugged in to a hub with addresses you had assigned - they would need the same mask to talk.

    As Pete has pointed out, the Internet is a classic example of all different networks talking to each other due to routing.

    Regards

    Si
     
    Certifications: MCSA 2003, MCDST, A+, N+, CTT+, MCT
  7. Raffaz

    Raffaz Kebab Lover Gold Member

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    Cheers for the info :)
     
    Certifications: A+, MCP, MCDST, AutoCAD
    WIP: Rennovating my house

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