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IP funky story

By neolongfellow ·
I'm working with and managing severarl IT Pro's, one of them, during the discussion of a class "a" block of IP addresses informed me that in the internet all ip's are considered class "c" in spite of their default mask. That was kind of confusing to me and didn't make sense. Am I missing something here or is he trying to josh me?

Thank you.

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by jamil_lababidi In reply to IP funky story

in your post, you referenced:

"in the internet all ip's are considered class "c" in spite of their default mask."

this is not true. there are 5 different classes of IP addresses, which i will explain. the first 3 digits (8 bits) of an IP address will tell you exactly what class an IP address is.

class A 1.x.x.x - 126.x.x.x

(127 is reserved for loopback)

class B 128.x.x.x - 1**.x.x.x
class C 192.x.x.x - 223.x.x.x
class D 224.x.x.x - 247.x.x.x

(class D is used for multicast addresses though)

class E 248.x.x.x - 255.x.x.x

(class E is reserved for experimental use)

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negative pt. 2

by jamil_lababidi In reply to IP funky story

in addition, classful IP addresses are slowly fading out of the picture, and CIDR (Classles InterDomain Routing) is coming into the schema of everything.. in a short story, CIDR is taking full advantage of subnetting subnets and so on..

hopethis information was helpful.

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by DukeBytes In reply to negative pt. 2

I bet that he was talking about CIDR.

We still have classes of addresses - but by "super subnetting" them you can have several "class C" address from one class A.

10.x.x.x is a reserved class A address.

You can have this subnetteddown to a subnetted class C buy making the subnetmask for example - that would make it a 10.x.x.x/27 network in CIDR world.

It basically gave the ISP a lot more address to use instead of everyone having a whole class to themselves.


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Thank you

by neolongfellow In reply to CIDR

More than likely, this is what he must have been refering to. Can you further explain how a 10.x.x.x/27 in CIDR would reflect a class "C" address. Thank again.

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class c compare

by DukeBytes In reply to Thank you

A normal class C address would be something like this...

This is with the default subnet mask.

If you subnetted that it might look something like this...

That address would give you 2 subnets with 62 hosts per subnet.

If you took a Class A address and subnetted it down to a subnet mask it would be considered a /26 network (in the CIDR world)

And it could look like this...
So you are basically subnetting a class A address to a subnetted Class C address - or as they used to call it before CIDR came along - super subnetting.

Hope that helps,

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Thank you

by neolongfellow In reply to negative pt. 2

This certainly helped to clarify this issue. Much appreciated.

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Explanation needed

by timwalsh In reply to IP funky story

I would "challenge" your IT "Pro" to further explain what he meant by his ascertation.

He may have been trying to oversimplify an issue. But his statement may also point to a total misunderstanding of the subject on his part.

Jamil does a good job of explaining what determines the "class" of a particular IP address.

These days, the "class" of a particular block of IP addresses is really only important if you are taking a networking test. In the past it was important for those who assigned IP address blocks (ISPs, etc.) to understand the various classes.

At present, the fact is that there are no more COMPLETE Class A and Class B address blocks available for distribution. This doesn't prevent anyone from being assigned a block of addresses that consists of IP addresses in those classes.

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