Private LAN addresses

[Arcaneuk10]

Dear All

a question.

According to Wendell Odom-100-105 official cert guilde book.

class A address private IP networks- 10.0.0.0

class B address private IP networks- 172.16.0.0 - 172.31.0.0

class C address private IP networks- 192.168.0.0 - 192.168.255.0

On a respected web page, the values are:

class A	10.0.0.0 – 10.255.255.255
class B	172.16.0.0 – 172.31.255.255
class C	192.168.0.0 – 192.168.255.255

 which is the correct  value, I am asking this, because I am trying to answer below question

According to RFCs which of the following addresses are not private LAN addresses? (Choose Two)

  a)  172.31.1.1   b)  172.33.1.254   c)  192.168.2.0   d)  192.186.2.0

I make the answer to be c and d, based on wendell odom's book, can you assist?

many thanks

Arcaneuk10

[Julio E. Moisa]

Hi

The 172.33.1.254 is a public IP address. 

As you know the ranges are:

10.0.0.0 to 10.255.255.255 

172.16.0.0 to 172.31.255.255

192.168.0.0 to 192.168.255.255

So 172.33.1.254 is not part of none network above. It can considered as a Public IP address. 

And the second is D, because 192.186.2.0 is not a private IP by the second octet. That is a visual trick (a private IP is 192.168 no 192.186) 

So the answers should be B and D

Hope it is useful

:-) 

[Arcaneuk10]

Hi Julio

Thanks for the reply, I get that now, it makes sense to me if I follow the web page with the following:

10.0.0.0 to 10.255.255.255 

172.16.0.0 to 172.31.255.255

192.168.0.0 to 192.168.255.255

I did not understand it based on wendell odom's page, should I follow what the above ranges are, and not the wendell odom page on private lan ranges, because as you can see they are both different, I hope I am making sense here.

Regards

Arcaneuk10

[Julio E. Moisa · Accepted solution]

Hi 

I think it can be interpretated, based on your information the information is not wrong, because he is mentioning just the networks associated to these ranges, for example:

Networks into these ranges are:

Class A   10.0.0.0

Class B  172.16.0.0 to 172.31.0.0 

So you will have:  172.16.0.0/16

                            172.17.0.0/16

                             172.18.0.0/16

                              .

                              .

                              172.31.0.0/16

Class C  192.168.0.0 to 192.168.255.0 

basically the same like Class B

Now the other way to represent that is including all the networks along with the IP addresses into these ranges

Class A   10.0.0.0 to 10.255.255.255

Class B 172.16.0.0 to 172.31.255.255

Class C 192.168.0.0  to 192.168.255.255

Basically 

In Class A you can modify the Octet 2,3 and 4 but not the octet 1

in Class B you can modify the Octet 2,3,4 but not the octet 1 and you have restrictions with the octet 2 where you can modify them with values from 16 to 31, now 32 will not be part of this range.

in Class C you can modify the Octet 3 and 4. 

Hope it is useful

:-)

[Arcaneuk10]

Hi Julio

Thank you, that makes sense to me now.

very grateul for your help.

Regards

Arcaneuk10

[Julio E. Moisa · Accepted solution]

Hi

It was a pleasure my friend, have a great day.

:-)

[Arcaneuk10 · Accepted solution]

Hi Joseph

Many thanks, I do get it now, very grateful for the info, thank you.

Regards

Arcaneuk10

[Joseph W. Doherty]

(NB: Overlapping what's already been posted.)

Both lists are correct. The first is just listing classful network addresses, the latter is listing address ranges for those networks. For example, the classful (A) network 10.0.0.0 (or the CIDR 10.0.0.0/16) encompasses the address range 10.0.0.0 through 10.255.255.255.

Oh, and as Julio noted, the non-private IPs are answers B and D.