Subnet Mask division shortcuts

1. How many subnets will be generated

The X power of 2-2 (X represents the mask bit, that is, the part of the binary system that is 1. In the current network,-2 is no longer required and can be used in all, however, you need to add the corresponding configuration commands. For example, you can use all the commands by adding the IP subnet zero command to the Cisco router .)

Note: I have read a lot of books, and now the number of subnets does not need to be subtracted from 2, so it is OK to directly power 2 to the power of X!

2. Number of hosts

The power of Y of 2-2 (Y represents the host bit, that is, the part with the hexadecimal value 0)

3. valid subnet is

Valid subnet mask = 256-10 (block size or base number)

4. The subnet broadcast address is

Broadcast address = subnetwork ID-1

5. Valid hosts are

The valid host address is ignored. The last valid host address = the next subnet number-2 (that is, the broadcast address-1)

Example:

Class C address: The network address 192.168.10.0. The subnet mask 255.255.255.192 (/26) calculates the number of subnets, number of hosts, valid subnets, broadcast addresses, and valid host ranges.

Number of subnets: 2*2 = 4

Number of hosts: 2*6-2 = 62

Valid subnets: 256-192 = 64 192.168.10.0 192.168.10.64 192.168.10.128 192.168.10.192

Broadcast address: 192.168.10.63 192.168.10.127 192.168.10.191 192.168.10.255

Valid host range: 192.168.10.1 ~ 192.168.10.62 192.168.10.65 ~ 192.168.10.190 192.168.10.193 ~ 192.168.254