Find the network address and broadcast address of the IP address, and the number of hosts

The easy way to record:

Example: 100.102.10.20/27

Step 1: Convert the subnet mask

27  ==》 255.255.255.224

Step 2: What we need to deal with is where the subnet mask is not 255, so calculate the 224 part

因为0-255有256个，所以用256-224=32 ==>2^5从最后一段借了3位

Step 3: You can see the network bit:

从0开始划分： 0,32,64,96,128,160,192,224,256

Step 4: Compare which part of the last digit of the IP address is divided in the third step:

20  ==》  0 - 32 之间

Step 5: It can be deduced that:

网络地址为： 100.102.10.0

广播地址为：100.102.10.31（32是下一个网段的网络地址，所以需要减1）

Other examples:

10.145.129.20/21
Network address: 10.145.128.0
Broadcast address: 10.145.135.255