For us to subnet very well both in real world and in CCNA exam it is important that you get conversant with subnet mask in octect form, bit form, binary form and also in slash notions. Finally, using some sort of formula can help in saving time while solving subnetting questions in CCNA exams. In this tutorial we are going to explore all these , it might be length but it’s worth reading through.
11111111.0000000.00000000.00000000 =255.0.0.0 in slash notion we have slash /8 hence we have
11111111.11111111.10000000.00000000 =255.255.128.0/17 17bits on
11111111.11111111.11000000.00000000 =255.255.192.0/18 18 bits on.
11111111.11111111.11100000.00000000 =255.255.224.0/19 19 bits on
11111111.11111111.11110000.00000000 = 255.255.240.0/20 20bit on.
11111111.11111111.11111000.00000000 = 255.255.248.0/21 21 bits on.
11111111.11111111.11111100.00000000 = 255.255.252.0/22 22 bits on.
11111111.11111111.11111110.00000000 = 255.255.254.0/23 23 bits on
11111111.11111111.11111111.00000000 = 255.255.255.0/24 24 bits on
11111111.11111111.10000000.00000000 =255.255.255.128 /25 25bits on
11111111.11111111.11000000.00000000 =255.255.255.192/26 26 bits on.
11111111.11111111.11100000.00000000 =255.255.255.224/27 27 bits on
11111111.11111111.11110000.00000000 = 255.255.255.240/28 28bit on.
11111111.11111111.11111000.00000000 = 255.255.255.248/29 29 bits on.
11111111.11111111.11111100.00000000 = 255.255.255.252/30 30 bits on.
11111111.11111111.11111110.00000000 = 255.255.255.255/31 31 bits on
With this in place and in mind you can be very fast while creating network and host on your network even in your CCNA exam another method to determine the number of host and networks in while building a network is t use this mathematical formular (2*) where * is equal to the number of bits, with this you can find your network ranges. (2*)-2 with this fromular you can find your network host ranges. We will be solving with this formular in our upcoming post.