Re: Understanding IP class range.

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Author: Keith Smith
Date:  
To: Main PLUG discussion list
Subject: Re: Understanding IP class range.

Very nice Kenn!!

Ok so if I had 192.168.1.0/25 the range would be 192.168.1.0 -
192.168.1.127

/26 would be 192.168.1.0 - 192.168.1.192 ? or is it 192.168.1.0 -
192.168.1.64 ?

Is that correct?

Not sure how to make a net mask out of 192.168.1.0/25 - would it be
255.255.255.128?


Thanks!!


On 2015-08-31 02:55, wrote:
> Hi Keith,
>
> If I recall correctly, the /24 part of 192.168.0.0/24 is the subnet
> specified in CIDR notation (Classless Inter Domain Routing).
>
> Think in binary terms, that /24 equals
> 11111111.11111111.11111111.00000000 (note there's 24 1's) equals
> 255.255.255.0 so is a class C subnet with the first three octets being
> the network mask.
>
> Likewise if you had an IP addy followed by a /8 that equals
> 11111111.00000000.00000000.00000000 equals 255.0.0.0 so is a class A
> subnet.
>
> Called octets cuz there's 8 bits hence a decimal max of 255.
>
> CIDR is usually seen at ISP's or in enterprise networks that need to
> subnet further as the network mask does not have to align with the
> octet boundary as it does in the classfull network addressing we're
> used to. That's where things get weird and all this because those
> silly routers only speak binary. :]
>
> If you're seeing 192.168.0.0/24 in a zenmap target field it means scan
> everything from and including 192.168.0.0 to 192.168.0.255.
>
>
> IP network classes or Classfull Network Addressing
>
>     - Range -                        - mask -        # of networks    # of nodes    CIDR mask
> A    1.1.1.1 -     126.255.255.255        255.0.0.0        126                16,777,214    /8
> B    128.0.0.1 - 191.255.255.255        255.255.0.0        16,384            65,534        /16
> C    192.0.0.1 - 223.255.255.255        255.255.255.0    2,097,151        254            /24
> D    224.0.0.1 - 239.255.255.255
> E    240.0.0.1 - 255.255.255.255

>
>
>
> --Kenn
>
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--
Keith Smith
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