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  1. Junior Member
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    #1

    Default Valid Private IP Address?

    I am somewhat new to networking and I am currently enrolled in the CNAP through a local community college. I have a question that may seem somewhat "dumb". Is 192.168.0.0 a valid private IP address? The reason I am asking is because my instructor says it is, but I thought that if the last two octets of an address were set to 0, then that specified a network address for a class B network. My instructor said that the address can be used as a address range for 254 hosts; 192.168.0.1-192.168.0.254. I just don't understand why the third octet is allowed to be 0 in a class C address range. If anyone could clarify I would very much appreciate it.
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  3. Johan Hiemstra Forum Admin Webmaster's Avatar
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    #2
    It is a valid IP address, not a valid host address though.

    The reason the third octet can be 0, is the subnet mask of a class C address: 255.255.255.0, this makes 192.168.0.0 a different network than 192.168.1.0.

    As you can read here:
    http://rejsy-morskie.com/?page=technotes/n...pipsuite.shtml

    if the first octet is 192 through 223, the address is a class C address, which uses the class C subnet mask, 255.255.255.0 by default.
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  4. Junior Member
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    #3
    OK, I think I got it. The last octet in the network portion of a class B or C address can be set to 0 because the subnet mask specifies that octet as part of the nework identifier. So in effect, with the exception of the first octet in a class B or C network address, the following network portion octects or octet can be between 0 - 255? For example, a valid range of class B network addresses could be 128.0.0.0 - 191.255.0.0, with a subnet mask of 255.255.0.0 and a valid range of class C network addresses could be 192.0.0.0 - 223.255.255.0 with a subnet mask of 255.255.255.0. Is this correct?
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