Subnet and Broadcast Address

Subnet and Broadcast Address

Class A

Class B

Class C

Example 1:
What is the broadcast and network address for host 112.48.160.183 255.255.255.192 ?
Example 2:
What subnet and broadcast address is the IP address 172.16.40.255/20 a number of?
Example 3:
What subnet and broadcast address is the IP address 172.16.40.14/30 a number of?
Example 4:
What subnet and broadcast address is the IP address 172.16.50.45/19 a number of?
Example 5:
What is the subnet and broadcast address of the host 172.16.80.255/20?
Example 6:
What is the broadcast and network address for host 222.129.199.222/21?
Example 7:
What is the broadcast address and network for station 192.168.99.77/19 ?

Class A

Example 1:

What is the broadcast and network address for host 112.48.160.183 255.255.255.192 ?

Solution:

  Class  A addresses use a default mask of 255.0.0.0
  Given subnet mask = 255.255.255.192 
  Valid subnets = 256 – 192 = 64, which means we have a block
  size of 64 in the forth octet.
  Count by 64 until  reaching  183.
  Subnets are 0, 64, 128,  192 etc. 
  Address 183 falls  in the 128 subnet.
  Subnet = 112. 48. 160. 128
  Next subnet address = 112. 48. 160. 192/26
  Broadcast address is 112. 48. 160. 191/26 of 112. 48. 160. 128
  network.
  The broadcast address is: 112. 48. 160. 191
    

Class B

Example 2:

What subnet and broadcast address is the IP address 172.16.40.255/20 a number of?

Solution:

  Class  B addresses use a default mask of 255.255.0.0
  Given subnet mask = 255.255.240.0 
  Valid subnets = 256 – 240 = 16, which means we have a block
  size of 16 in the third octet.
  Count by 16 until  reaching  40.
  Subnets are 0, 16, 32,  48 etc. 
  Address 40 falls  in the 32 subnet.
  Subnet = 172. 16. 32. 0 
  Next subnet address = 172. 16. 48. 0/20
  Broadcast address is 172. 16. 47. 255/20 of 172. 16. 32. 0/20
  network.
  The broadcast address is: 172. 16. 47. 255
  

Example 3:

What subnet and broadcast address is the IP address 172.16.40.14/30 a number of?

Solution:

  Class  B addresses use a default mask of 255.255.0.0
  Given subnet mask = 255.255.255.252(/30)
  Valid subnets = 256 – 252 = 4, which means we have a block
  size of 4 in the forth octet.
  Count by 4 until  reaching  14.
  Subnets are 0, 4, 8,  12, 16 etc.
  Address 14 falls  in the 12 subnet.
  Subnet = 172. 16. 40. 12
  Next subnet address = 172.  16. 40. 16/30
  Broadcast address is 172.  16. 40. 15/30 of 172.  16. 40. 12/30
  network.
  The broadcast address is: 172. 16. 40. 15
  

Example 4:

What subnet and broadcast address is the IP address 172.16.50.45/19 a number of?

Solution:

  Class  B addresses use a default mask of 255.255.0.0
  Given subnet mask = 255.255.224.0 (/19)
  Valid subnets = 256 – 224 = 32, which means we have a block
  size of 32 in the third octet.
  Count by 32 until  reaching  50.
  Subnets are 0, 32, 64  etc.
  Address 50 falls  in the 32 subnet.
  Subnet = 172. 16. 32. 0
  Next subnet address = 172. 16. 64. 0/19
  Broadcast address is 172. 16. 63. 255/19 of 172. 16. 32. 0/19
  network.
  The broadcast address is: 172. 16. 63. 255
  

Example 5:

What is the subnet and broadcast address of the host 172.16.80.255/20?

Solution:

  Class  B addresses use a default mask of 255.255.0.0
  Given subnet mask = 255.255.240.0  (/20)
  Valid subnets = 256 – 240 = 16, which means we have a block
  size of 16 in the third octet.
  Count by 16 until  reaching  80.
  Subnets are 0, 16, 32,  48, 64, 80, 96 etc.
  Address 80 falls  in the 80 subnet.
  Subnet = 172. 16. 80. 0
  Next subnet address = 172. 16. 96. 0/20
  Broadcast address is 172. 16. 95. 255/20 of 172. 16. 80. 0/20
  network.
  The broadcast address is: 172. 16. 95. 255
  

Class C

Example 6:

What is the broadcast and network address for host 222.129.199.222/21?

Solution:

 Class  C addresses use a default mask of 255.255.255.0
  Given subnet mask = 255.255.248.0  (/21)
  Valid subnets = 256 – 248 = 8, which means we have a block
  size of 8 in the third octet.
  Count by 8 until  reaching  199.
  Subnets are 0, 8, 16, …  , 184, 192, 200, etc.
  Address 199 falls  in the 192 subnet.
  Subnet = 222. 129. 192. 0
  Next subnet address = 222. 129. 200. 0/21
  Broadcast address is 222.129.199.255/21 of 222.129.192.0/21
  network.
  The broadcast address is: 222. 129. 199. 255
  

Example 7:

What is the broadcast address and network for station 192.168.99.77/19?

Solution:

  Class  C addresses use a default mask of 255.255.255.0
  Given subnet mask = 255.255.224.0 (/19)
  Valid subnets = 256 – 224 = 32, which means we have a block
  size of 32 in the third octet.
  Count by 32 until  reaching 99.
  Subnets are 0, 32, 64,  96, 128 etc.
  Address 99 falls  in the 96 subnet.
  Subnet = 192. 168. 96. 0
  Next subnet address = 192. 168. 128. 0/19
  Broadcast address is 192. 168. 127. 255/19 of 192. 168. 96. 0/19
  network.
  The broadcast address is: 192. 168. 127. 255