Azure Classroom Series – 18/Aug/2021

Networking Fundamentals continued

• Possible subnet mask’s as per what we understood yesterday

SM => 255.255.255.0 => Host (1 Octet) => 2^8 ~= 256
   => 255.255.0.0 => Host (2 octets) => 2^16 ~= 65536
   => 255.0.0.0 => Host (3 Octets) => 2^24 ~= 16777216

• Lets assume i need a network

  • with 200 devices => SM => 255.255.255.0
  • with 500 devices => SM => 255.255.0.0

• Now lets look at networks. A network can be regarded as one of the following types

  • Classful networks
  • Classless networks

• Classful Networks:

  • In terms of classfull networks we have five classes
    • A
    • B
    • C
    • D
    • E

• Class D compromises of range of IP addresses that are set aside for multicast transmission purpose 224.0.0.0 - 239.255.255.255

• Class E is set aside for expermimental purposes 240.0.0.0 - 255.255.255.255

• Classles Inter Domain Routing (CIDR)

  • This was introduced to replace classfull addresses. It uses variable length subnet masks
  • This has introduced a CIDR notation

• Subnet mask in binary

SM in binary:
   255.255.255.0
   11111111.11111111.11111111.00000000 => 8 zeros => 2^8 -2 => 254

       
   
   11111111.11111111.11111110.00000000 => 9 zeros => 2^ 9 -2 => 512 - 2 => 510
   
   
   100 devices => 2^n ~= 100  => n = 7 i.e 7 zeros
   
   11111111.11111111.11111111.10000000 => 7 zeros => 2^7-2 => 126
   
   1500 devices
   
   11111111.11111111.11111000.00000000 => 2^11 = 2046

• Possible SM’s in a octect

11111111 => 255
11111110 => 254
11111100 => 252
11111000 => 248
11110000 => 240
11100000 => 224
11000000 => 192
10000000 => 128

• The CIDR notation denotes subnet mask by /X

192.168.0.0/24
SM => 255.255.255.0
ip range 192.168.0.0 - 192.168.0.255

192.168.0.0/16
SM => 255.255.0.0
ip range => 192.168.0.0 - 192.168.255.255

192.168.0.0/23
SM => 255.255.254.0

192.168.0.0/23

11111111.11111111.11111110.00000000

11000000.10101000.0000000 0.00000000 => 192.168.0.0
11000000.10101000.0000000 1.11111111 => 192.168.1.255

10.10.128.0/22  => 32 -22 => 10 => 2^10 -2 => 1022

SM => 11111111.11111111.11111100.00000000

IP => 00001010.00001010.100000 00.00000000 => 10.10.128.0

      00001010.00001010.100000 11.11111111 => 10.10.131.255

• Exercise: Try to find the ip ranges for the following CIDR notations

172.16.0.0/12
192.168.0.0/16
10.0.0.0/8

10.100.192.0/20
10.10.0.0/21