Ytdyklly

1)Subnetting and Supernetting can both be done for private and public IP addresses?

2)Classful addresses weren't successful because of IP wasting,and that is why the 'network mask' was invented,correct?

3)Computers in classful networks all had public IP addresses,which led to IP wasting.The question here is: Does this still exist nowadays?

Any answers are highly appreciated!

Thank you.

1)Subnetting and Supernetting can both be done for private and public
IP addresses?

Yes. To the computer there is no distinction between public and private. They are all IP addresses.

2)Classful addresses weren't successful because of IP wasting,and that
is why the 'network mask' was invented,correct?

Not quite. The network mask defines which part of the address is the network address and which part is the host address.

3)Computers in classful networks all had public IP addresses,which led
to IP wasting.The question here is: Does this still exist nowadays?

The private addresses (RFC1918) existed with classful addressing. So, no, not all computers had public addresses. The situation is the same now: public (globally routable) addresses are used on the Internet, but many (most?) internal networks have private address configured internally and use address translation when communicating over the Internet.

1)Subnetting and Supernetting can both be done for private and public
IP addresses?

Yes. There is no IP distinction between private or public IP addresses. The private addresses were chosen somewhat arbitrarily, and only by ISP agreement are they blocked from being routed on the public Internet. Other than that, there is no inherent difference.

2)Classful addresses weren't successful because of IP wasting,and that
is why the 'network mask' was invented,correct?

Classful addresses are wasteful because only the full class could be routed on the Internet. They could be subnetted inside the entity that owned a classful network. Masks existed before VLSM and CIDR.

3)Computers in classful networks all had public IP addresses,which led
to IP wasting.The question here is: Does this still exist nowadays?

I'm not sure I quite understand the question. Network classes no longer exist, but there are entities that had been assigned a classful network and still have the entire block that had been assigned during the time we had classful networks.

I think it is important to understand that you cannot really have an efficient method of assigning IP addresses. There have been studies and math to back that up. That is one of the reasons that IPv6 was designed from the beginning to waste addresses.

About #2 question:
My book clearly says the following : "Beyond the waste and exhaustion of the available addresses, ...(more problems)
. To overcome such problems, it is done
systematic and specialized use of the network mask.

So i thought,that thanks to the mask we no longer need classes

About #3:

So Public IP addresses can be given to computers,not only to routers.How can this be done?

Last,i want help with the following example:

If an organisation with 1000 computers was given a Class B network,then every computer by standard(!) would have a public IP address.So a lot of these addresses will remain unused and wasted.Thanks to the introduction of the mask,the organisation could be given a subnet of that network with fewer computers.

Is this way how it works?