Why does the decrease of the subnet mask fold the size of the original network?

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Reading about IP protocol and network addressing, I don’t understand why the "diminishing" the size of the subnet mask in 1 bit, generates a "augmentation" network size.

I understood the reason for the increase, but not the fact of the decrease of 1 bit double the increase.

The reverse is also true according to the source of ppgia. porque

Assertion of the author

The process of grouping subnets is also simple. Each time we decrease the size of the subnet mask by 1 bit, we create a super-net that is twice the size of the original network. In practice, the concept of super networks is quite useful to decrease the number of entries in the routing tables of routers on the Internet.

source: ppgia.pucpr.br

networks ip
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    I am voting to close this question as out of scope because networks, even data is not part of the scope of the site. I am not against it, as long as it is not procaria, I believe it does the community good, but so far it is not allowed.

  • Okay, I appreciate the feedback.

  • @Stormwind I tend to agree, but I think this question can be considered within the scope of the site. https://answall.com/help/on-topic has a list of five items, I think this question fits at least the last two.

  • We will see how this question and its answers unfold @Renan

1 answer

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The mask is made to separate the network part from the host part.

The bits worthwhile 1 represent the part of the network, while the bits worthwhile 0 represent the host part. And are these bits worthwhile 0 that are used to generate unique Ips of hosts.

This is worth explaining the notation /24, /25, etc. This notation counts the number of 1 consecutive in the mask.

The fact of increasing/decreasing 1 bit decrease by half/double the network size is natural of binary representation. The network size is given by 2^(32-mascara).

An illustrative example.

Mascara:    255.255.255.0 = 24  11111111.11111111.11111111. 00000000

Soon we have the last 8 bits available, 2 8 = 256 Ips.

If we use the mask /23:

Mascara:    255.255.254.0 = 23  11111111.11111111.1111111 0.00000000

Now we have the last nine bits available. 2 9 = 512 Ips. Double the previous.

  • Then you "decrease" the representative amount of the mask to "increase" in the amount representing the host, I thank you for answering, this number /23 or /22 at the end of the ip became much clearer now.

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