N+ - IP Range Classes - Question?

[Plazmadawg]

Hi guys Plazmadawg here,

I currently studying my N+ and have been enjoying it very much.

I am a little confused on the classes, as I have seen other IP addresses that do not fit that range charts for example:

Lets say I have an IP address 10.197.23.x and my subnet is 255.255.254.0... I have no idea what class this would be classified as?

As per the below table, I would assume my IP class is a class A network if I looked at the private IP range however the subnet mask doesn't correspond with a class A network.



Therefore I am very confused on how to class an IP address 10.197.23.x and subnet mask of 255.255.254.0.

Any network guru's out there that can help shed some light on my question?

thanks guys

 

[Mr Scratch]

/23 class C?

 

[Plazmadawg]

/23 class C?

Hi Waylander

I did establish that it is /23 however I am having great difficulty figuring out what class it is.

As what I understand is that if it your ip range is between 10.0.0.0.0 - 10.255.255.255 it would make it a class A network, 10.197.23.x would fall within that range making it a class A network or am I misunderstanding something?

 

[Nuke]

Class A, B and C (also D and E while we are at it) has not been used in many years as a classification. While you still may find a few people talking about a class C when they mean a netmask of 255.255.255.0 its just a point of interest nowadays. Classless routing has been around for 25 years, as long as you have the IP and netmask (or netmask and first IP of the range if you are doing routing) you are good to go.

Back then 10.197.23.x would have gone with a mask of 255.0.0.0 and be a Class A, not 255.255.254.0

 

[SauRoNZA]

Technically anything with a first octet 1 - 126 would be Class A.

But as Nuke says above it's really all theory bull**** and kind of meaningless and just about anything would work anywhere if it was actually put on the internet.

Here are two tools to make your life easier...or confuse you even more.

http://www.subnet-calculator.com/subnet.php?net_class=A

http://www.subnet-calculator.com/cidr.php

Out of interest are you using a very old N+ book and doing this yourself? Or does the current curriculum really still cover this stuff?

 

[Plazmadawg]

Class A, B and C (also D and E while we are at it) has not been used in many years as a classification. While you still may find a few people talking about a class C when they mean a netmask of 255.255.255.0 its just a point of interest nowadays. Classless routing has been around for 25 years, as long as you have the IP and netmask (or netmask and first IP of the range if you are doing routing) you are good to go.

Back then 10.197.23.x would have gone with a mask of 255.0.0.0 and be a Class A, not 255.255.254.0

oh okay I see.

Thank you for that

So if I understand correctly, classes are a bit out dated thus we do not really classify them as such any longer?

I am battling to understand the following tables, I understand the first table, with regards to the amount of networks and hosts however the Private IP Addresses are confusing me and I am not sure when those classes apply.

Could you provide any clarification on that?

 

[Plazmadawg]

Technically anything with a first octet 1 - 126 would be Class A.

But as Nuke says above it's really all theory bull**** and kind of meaningless and just about anything would work anywhere if it was actually put on the internet.

Here are two tools to make your life easier...or confuse you even more.

http://www.subnet-calculator.com/subnet.php?net_class=A

http://www.subnet-calculator.com/cidr.php

Out of interest are you using a very old N+ book and doing this yourself? Or does the current curriculum really still cover this stuff?

Hi SauRoNZA

I am currently using the Sybex N+ Studying Guide 3rd Edition N10-006 book by Todd Lammie and using some videos to help me understand it. Yes, it still covers the classes and I will most likely see it in the exam thus I am worried about it as I am battling to understand it.

It just sounds extremely important and I am struggling to understand it.

Edit: Thank you for the links

 

[Nuke]

oh okay I see.

Thank you for that

So if I understand correctly, classes are a bit out dated thus we do not really classify them as such any longer?

I am battling to understand the following tables, I understand the first table, with regards to the amount of networks and hosts however the Private IP Addresses are confusing me and I am not sure when those classes apply.

Could you provide any clarification on that?

The only really important part of the table is this:
"addresses 127.0.0.0 to 127.255.255.255 cannot be used and is reserved for loopback and diagnostic functions"
"10.0.0.0 - 10.255.255.255"
"172.16.0.0 - 172.31.255.255"
"192.168.0.0 - 192.168.255.255"
And knowing you use those 3 ranges for your internals networks. They have no difference between them, except address space.

Also about multicast and its range is good to know of, but except for if you find multicast very interesting, just remember about it. Likely the first time you will see it used is with routing protocols, and you will learn about it then.

The rest is history, interesting history nonetheless, but not much use in everyday work. Wiki has a good summery https://en.wikipedia.org/wiki/Classful_network

 

[Mr Scratch]

Don't make the error of thinking 192.168.0.0 is /8 like 10.0.0.0/8, because it's 192.168.0.0/16

I've seen this happen in real life.

 

[Genisys]

Don't make the error of thinking 192.168.0.0 is /8 like 10.0.0.0/8, because it's 192.168.0.0/16

I've seen this happen in real life.

And 172.16.0.0/12 is also an option. 172.0.0.0/8 puts you in public space again.

 

[gregmcc]

classful addresses take some getting used to. Wait till you see a valid address ending in .0 or .255

 

[Rickster]

I think what they call class C in that picture is wrong, it should be 192.168.0.0 - 192.168.0.255 Subnet mask 255.255.255.0

 

[irBosOtter]

I think what they call class C in that picture is wrong, it should be 192.168.0.0 - 192.168.0.255 Subnet mask 255.255.255.0

picture is 100% correct

 

[syntax]

oh okay I see.

Thank you for that

So if I understand correctly, classes are a bit out dated thus we do not really classify them as such any longer?

I am battling to understand the following tables, I understand the first table, with regards to the amount of networks and hosts however the Private IP Addresses are confusing me and I am not sure when those classes apply.

Could you provide any clarification on that?

The table explains itself, in classful addressing, anything matching the first octet of those numbers fall into that class.
The private space is mentioned because this is not routed between ISP's for normal internet traffic. That means, these subnets can be re-used multiple times in private networks and therefore save public address space.
Classful addressing became wasteful, so VLSM was introduced to break this up further and divide IP space further. This helped reduce IP exhaustion to a point, however there were still some rules, the full BGP feed will not contain subnets smaller than /24's. This is to reduce load on the internet routers and improve convergence, if this was to be broken down further, the global table would explode.

classful addresses take some getting used to. Wait till you see a valid address ending in .0 or .255

we use this as an interview question, /23 subnet, is the 255 IP address of the first "/24" a usable IP

I think what they call class C in that picture is wrong, it should be 192.168.0.0 - 192.168.0.255 Subnet mask 255.255.255.0

It is correct, what you have there is a single subnet in the Class C range. If your example were the case, we would only have a single Class C subnet available, being 192.168.0.0/24, which is not the case