Understanding IP class range.

[Keith Smith]

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, parabellum7 at yahoo.com 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