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Subnetting aggregation

I saw this example online .

192.168.12.0/23 applies the network mask 255.255.254.0 to the 192.168 network, starting at 192.168.12.0. This notation represents the address range 192.168.12.0 - 192.168.13.255.

How do I obtain the applicable address range ?

Here's my understanding (most likely flawed) of the 192.168.12.0/23 CIDR IP address :

  1. /23 written in bits is 11111111.11111111.11111110.00000000 .
  2. Therefore, it "borrowed" 7 bits from the host field.
  3. 2^7 = 128 subnets being created.
  4. 2^1 = Each subnet has a maximum of 2 hosts.
  5. There are 128 possible network IDs, possible ones are 192.168.0.0, 192.168.170.0 192.168.254.0.
  6. The range of ip addresses are from 192.168.0.0 to 192.168.254.0 ?