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The Red Hat version of the ipcalc program is very basic compared with some other versions that are available.

Suppose you didn't have an internet connection and could only use tools that exist within RHEL - what references or tools could help you to calculate subnet information for a variety of ip addresses in various classes?

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I use a smartphone application. side steps the issue entirely, unless you need the info for a script of some sort ? Also, class based IPs disappeared a long long time ago. – Sirex Apr 29 '13 at 0:15
For most cases, its not that difficult to do it in your head if you (a) understand how binary converts to decimal and (b) can memorise the sequence 1,2,4,8,16,32,64,128,256 !! – davidgo Apr 29 '13 at 1:05

I usually just do it in my head now or if I'm really having a bad day I use a smartphone app. But I still have this handy chart stapled to my wall: (

It gives me everything I could ever really need to know about subnets /24-/30

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