First Valid Host Address

First Valid Host Address

Class A

Example 1:
What is the first valid host on the subnetwork that the node 10.42.229.102 255.255.240.0 belongs to?
Example 2:
What is the first valid host on the subnetwork that the node 10.125.213.141 255.255.240.0 belongs to?
Example 3:
What is the first valid host on the subnetwork that the node 10.245.110.177/20 belongs to?
Example 4:
What is the first valid host on the subnetwork that the node 172.17.58.198/25 belongs to?
Example 5:
What is the first valid host on the subnetwork that the node 172.17.210.72 255.255.255.240 belongs to?
Example 6:
What is the first valid host on the subnetwork that the node 172.17.231.153 255.255.255.224 belongs to?
Example 7:
What is the first valid host on the subnetwork that the node 172.18.74.129/22 belongs to?
Example 8:
What is the first valid host on the subnetwork that the node 172.18.88.10 255.255.255.192 belongs to?
Example 9:
What is the first valid host on the subnetwork that the node 172.18.192.21/28 belongs to?
Example 10:
What is the first valid host on the subnetwork that the node 172.19.136.151/23 belongs to?
Example 11:
What is the first valid host on the subnetwork that the node 172.19.247.58/21 belongs to?
Example 12:
What is the first valid host on the subnetwork that the node 172.20.163.58/22 belongs to?
Example 13:
What is the first valid host on the subnetwork that the node 172.20.182.215 255.255.255.128 belongs to?
Example 14:
What is the first valid host on the subnetwork that the node 172.21.203.90 255.255.252.0 belongs to?
Example 15:
What is the first valid host on the subnetwork that the node 172.23.69.177/23 belongs to?
Example 16:
What is the first valid host on the subnetwork that the node 172.24.4.47 255.255.255.224 belongs to?
Example 17:
What is the first valid host on the subnetwork that the node 172.24.109.166/23 belongs to?
Example 18:
What is the first valid host on the subnetwork that the node 172.24.252.1/26 belongs to?
Example 19:
What is the first valid host on the subnetwork that the node 172.25.118.106 255.255.255.0 belongs to?
Example 20:
What is the first valid host on the subnetwork that the node 172.26.170.136/23 belongs to?
Example 21:
What is the first valid host on the subnetwork that the node 172.27.58.38 255.255.255.0 belongs to?
Example 22:
What is the first valid host on the subnetwork that the node 172.28.36.65/28 belongs to?
Example 23:
What is the first valid host on the subnetwork that the node 172.28.176.50/24 belongs to?
Example 24:
What is the first valid host on the subnetwork that the node 192.168.21.153/27 belongs to?
Example 25:
What is the first valid host on the subnetwork that the node 192.168.26.249/27 belongs to?
Example 26:
What is the first valid host on the subnetwork that the node 192.168.51.193/26 belongs to?
Example 27:
What is the first valid host on the subnetwork that the node 192.168.94.150/26 belongs to?

Class A

Example 1:

What is the first valid host on the subnetwork that the node 10.42.229.102 255.255.240.0 belongs to?

Solution:

  Class A addresses use a default mask of  255.0.0.0.
  Given subnet mask = 255.255.240.0 

  Block size = 256 - 240 = 16,  which means we have a block size
  of 16 in the third octet.
  Valid Subnets =  0, 16, … , 224, 240.
  Thus subnet = 10.42.224.0
  The first valid host IP = 10.42.224.1
    

Example 2:

What is the first valid host on the subnetwork that the node 10.125.213.141 255.255.240.0 belongs to?

Solution:

  Class A addresses use a default mask of  255.0.0.0.
  Given subnet mask = 255.255.240.0
  Block size = 256 - 240 = 16,  which means we have a block size
  of 16 in the third octet.
  Valid Subnets = 0, 16, … , 208, 224, 240
  Thus subnet = 10.125.208.0
  The first valid host IP = 10.125.208.1
    

Example 3:

What is the first valid host on the subnetwork that the node 10.245.110.177/20 belongs to?

Solution:

  Class A addresses use a default mask of 255.0.0.0.
  Given subnet mask = 255.255.240.0
  Block size = 256 - 240 = 16,  which means we have a block size
  of 16 in the third octet.
  Valid Subnets = 0, 16, … ,80,96,112, … , 224, 240.
  Thus subnet = 10. 245. 96. 0
  The first valid host IP = 10. 245. 96. 1
    

Class B

Example 4:

What is the first valid host on the subnetwork that the node 172.17.58.198/25 belongs to?

Solution:

  Class B addresses use a default mask of 255.255.0.0.
  Given subnet mask = 255.255.255.128
  Block size = 256 - 128 = 128,  which means we have a block size
  of 128 in the forth octet.
  Valid Subnets = 0, 128.
  Thus subnet = 172. 17. 58. 128
  The first valid host IP = 172. 17. 58. 129
    

Example 5:

What is the first valid host on the subnetwork that the node 172.17.210.72 255.255.255.240 belongs to?

Solution:

  Class B addresses use a default mask of 255.255.0.0.
  Given subnet mask = 255.255.255.240
  Block size = 256 - 240 = 16,  which means we have a block size
  of 16 in the forth octet.
  Valid Subnets = 0, 16, 32, 48, 64, 80, … , 240.
  Thus subnet = 172. 17. 210. 64
  The first valid host IP = 172. 17. 210. 65
    

Example 6:

What is the first valid host on the subnetwork that the node 172.17.231.153 255.255.255.224 belongs to?

Solution:

  Class B addresses use a default mask of 255.255.0.0.
  Given subnet mask = 255.255.255.224
  Block size = 256 - 224 = 32,  which means we have a block size
  of 32 in the forth octet.
  Valid Subnets = 0, 32, 64, 96, 128, 160, .. , 224.
  Thus subnet = 172. 17. 231. 128
  The first valid host IP = 172. 17. 231. 129
    

Example 7:

What is the first valid host on the subnetwork that the node 172.18.74.129/22 belongs to?

Solution:

  Class B addresses use a default mask of 255.255.0.0.
  Given subnet mask = 255.255.252.0
  Block size = 256 - 252 = 4,  which means we have a block size
  of 4 in the third octet.
  Valid Subnets = 0, 4, … , 72, 76, … , 252.
  Thus subnet = 172. 18. 72. 0
  The first valid host IP = 172. 18. 72. 1
    

Example 8:

What is the first valid host on the subnetwork that the node 172.18.88.10 255.255.255.192 belongs to?

Solution:

  Class B addresses use a default mask of 255.255.0.0.
  Given subnet mask = 255.255.255.192
  Block size = 256 - 192 = 64,  which means we have a block size
  of 64 in the forth octet.
  Valid Subnets = 0, 64, … , 192.
  Thus subnet = 172. 18. 88. 0
  The first valid host IP = 172. 18. 88. 1
    

Example 9:

What is the first valid host on the subnetwork that the node 172.18.192.21/28 belongs to?

Solution:

  Class B addresses use a default mask of  255.255.0.0.
  Given subnet mask = 255.255.255.240
  Block size = 256 - 240 = 16,  which means we have a block size
  of 16 in the forth octet.
  Valid Subnets = 0, 16, 32, … , 240.
  Thus subnet =   172. 18.  192. 17
  The first valid host IP =  172. 18. 192. 17
    

Example 10:

What is the first valid host on the subnetwork that the node 172.19.136.151/23 belongs to?

Solution:

  Class B addresses use a default mask of 255.255.0.0.
  Given subnet mask = 255.255.254.0
  Block size = 256 - 254 = 2,  which means we have a block size
  of 2 in the third octet.
  Valid Subnets =. 0, 2, 4, 6, … ,134, 136, … , 254.
  Thus subnet = 172. 19. 136. 0
  The first valid host IP = 172. 19. 136. 1
    

Example 11:

What is the first valid host on the subnetwork that the node 172.19.247.58/21 belongs to?

Solution:

  Class B addresses use a default mask of 255.255.0.0.
  Given subnet mask = 255.255.248.0
  Block size = 256 - 248 = 8,  which means we have a block size of
  8 in the third octet.
  Valid Subnets = 0, 8, 16, 24, … , 232, 240, 248.
  Thus subnet = 172. 19. 240. 0
  The first valid host IP = 172. 19. 240. 1
    

Example 12:

What is the first valid host on the subnetwork that the node 172.20.163.58/22 belongs to?

Solution:

  Class B addresses use a default mask of 255.255.0.0.
  Given subnet mask = 255.255.252.0
  Block size = 256 - 252 = 4,  which means we have a block size
  of 4 in the third octet.
  Valid Subnets = 0, 4, 8, 12, … ,156,160,164, … ,  252.
  Thus subnet = 172. 20. 160. 0
  The first valid host IP = 172. 20. 160. 1
    

Example 13:

What is the first valid host on the subnetwork that the node 172.20.182.215 255.255.255.128 belongs to?

Solution:

  Class B addresses use a default mask of 255.255.0.0.
  Given subnet mask = 255.255.255.128
  Block size = 256 - 128 = 128,  which means we have a block size of
  128 in the forth octet.
  Valid Subnets = 0, 128.
  Thus subnet = 172. 20. 182. 128
  The first valid host IP = 172. 20. 182. 129
    

Example 14:

What is the first valid host on the subnetwork that the node 172.21.203.90 255.255.252.0 belongs to?

Solution:

  Class B addresses use a default mask of 255.255.0.0.
  Given subnet mask = 255.255.252.0
  Block size = 256 - 252 = 4,  which means we have a block size of 4
  in the third octet.
  Valid Subnets = 0, 4, 8, 12, … ,196, 200, 204, … ,  252.
  Thus subnet = 172. 21. 200. 0
  The first valid host IP = 172. 21. 200. 1
    

Example 15:

What is the first valid host on the subnetwork that the node 172.23.69.177/23 belongs to?

Solution:

  Class B addresses use a default mask of  255.255.0.0.
  Given subnet mask = 255.255.254.0
  Block size = 256 - 254 = 2,  which means we have a block size of
  2 in the third octet.
  Valid Subnets =. 0, 2, 4 , 6, … , 66, 68, … , 254.
  Thus subnet = 172. 23. 68. 0
  The first valid host IP = 172. 23. 68. 1
    

Example 16:

What is the first valid host on the subnetwork that the node 172.24.4.47 255.255.255.224 belongs to?

Solution:

  Class B addresses use a default mask of 255.255.0.0.
  Given subnet mask = 255.255.255.224
  Block size = 256 - 224 = 32,  which means we have a block size
  of 32 in the forth octet.
  Valid Subnets = 0, 32, 64, … , 224.
  Thus subnet = 172. 24. 4. 32
  The first valid host IP = 172. 24. 4. 33
    

Example 17:

What is the first valid host on the subnetwork that the node 172.24.109.166/23 belongs to?

Solution:

  Class B addresses use a default mask of 255.255.0.0.
  Given subnet mask = 255.255.254.0
  Block size = 256 - 254 = 2,  which means we have a block size
  of 2 in the third octet.
  Valid Subnets = 0, 2,4, … , 106,108, … , 254.
  Thus subnet = 172.  24. 108. 0
  The first valid host IP = 172. 24. 108. 1
    

Example 18:

What is the first valid host on the subnetwork that the node 172.24.252.1/26 belongs to?

Solution:

  Class B addresses use a default mask of 255.255.0.0.
  Given subnet mask = 255.255.255.192
  Block size = 256 - 192 = 64,  which means we have a block size
  of 64 in the forth octet.
  Valid Subnets = 0, 64, 128, 192.
  Thus subnet = 172. 24. 252. 0
  The first valid host IP = 172. 24. 252. 1
    

Example 19:

What is the first valid host on the subnetwork that the node 172.25.118.106 255.255.255.0 belongs to?

Solution:

  Class B addresses use a default mask of  255.255.0.0.
  Given subnet mask = 255.255.255.0
  Block size = 256 - 255 = 1,  which means we have a block size
  of 1 in the third octet.
  Valid Subnets = 0, 1,2, … , 117, 118, … , 255.
  Thus subnet =   172.25.118.0
  The first valid host IP = 172.25.118.1
    

Example 20:

What is the first valid host on the subnetwork that the node 172.26.170.136/23 belongs to?

Solution:

  Class B addresses use a default mask of 255.255.0.0.
  Given subnet mask = 255.255.254.0
  Block size = 256 - 254 = 2,  which means we have a block size
  of 2 in the third octet.
  Valid Subnets = 0, 2,4, … , 168, 170, 172, … , 254.
  Thus subnet = 172.  26. 170. 0
  The first valid host IP = 172. 26. 170. 1
    

Example 21:

What is the first valid host on the subnetwork that the node 172.27.58.38 255.255.255.0 belongs to?

Solution:

  Class B addresses use a default mask of 255.255.0.0.
  Given subnet mask = 255.255.255.0
  Block size = 256 - 255 = 1,  which means we have a block size
  of 1 in the third octet.
  Valid Subnets = 0, 1, 2, 3, … , 255.
  Thus subnet = 172.  27. 58. 0
  The first valid host IP = 172. 27. 58. 1
    

Example 22:

What is the first valid host on the subnetwork that the node 172.28.36.65/28 belongs to?

Solution:

  Class B addresses use a default mask of 255.255.0.0.
  Given subnet mask = 255.255.255.240
  Block size = 256 - 240 = 16,  which means we have a block size of
  16 in the forth octet.
  Valid Subnets =. 0, 16, 32, 48, 64, … , 240.
  Thus subnet = 172. 28. 36. 64
  The first valid host IP = 172. 28. 36. 65
    

Example 23:

What is the first valid host on the subnetwork that the node 172.28.176.50/24 belongs to?

Solution:

  Class B addresses use a default mask of 255.255.0.0.
  Given subnet mask = 255.255.255.0
  Block size = 256 - 255 = 1,  which means we have a block size of
  1 in the third octet.
  Valid Subnets =. 0, 1, 2, 3, … , 255.
  Thus subnet = 172.  28. 176. 0
  The first valid host IP = 172. 28. 176. 1
    

Class C

Example 24:

What is the first valid host on the subnetwork that the node 192.168.21.153/27 belongs to?

Solution:

  Class C addresses use a default mask of 255.255.255.0.
  Given subnet mask = 255.255.255.224
  Block size = 256 - 224 = 32,  which means we have a block size
  of 32 in the forth octet.
  Valid Subnets = 0, 32, 64, 96, 128, 160, … , 224.
  Thus subnet = 192.  168. 21. 128
  The first valid host IP = 192. 168. 21. 129
    

Example 25:

What is the first valid host on the subnetwork that the node 192.168.26.249/27 belongs to?

Solution:

  Class C addresses use a default mask of  255.255.255.0.
  Given subnet mask = 255.255.255.224
  Block size = 256 - 224 = 32,  which means we have a block size
  of 32 in the forth octet.
  Valid Subnets = 0, 32, 64, … ,192, 224.
  Thus subnet = 192.  168. 26. 224
  The first valid host IP = 192. 168. 26. 225
    

Example 26:

What is the first valid host on the subnetwork that the node 192.168.51.193/26 belongs to?

Solution:

  Class C addresses use a default mask of 255.255.255.0.
  Given subnet mask = 255.255.255.192
  Block size = 256 - 192 = 64,  which means we have a block size
  of 64 in the forth octet.
  Valid Subnets = 0, 64, 128, 192.
  Thus subnet = 192.  168. 51. 192
  The first valid host IP = 192. 168. 51. 193
    

Example 27:

What is the first valid host on the subnetwork that the node 192.168.94.150/26 belongs to?

Solution:

  Class C addresses use a default mask of 255.255.255.0.
  Given subnet mask = 255.255.255.192
  Block size = 256 - 192 = 64,  which means we have a block size of
  64 in the forth octet.
  Valid Subnets = 0, 64, 128, 192
  Thus subnet = 192.  168. 94. 128
  The first valid host IP = 192. 168. 94. 129
    

Exercise

Exercise 1:

What is the first valid host on the subnetwork that the node 172.29.18.32/25 belongs to?

Answer:

The first valid host IP = 172. 29. 18. 1

Exercise 2:

What is the first valid host on the subnetwork that the node 172.29.124.105 255.255.255.224 belongs to?

Answer:

The first valid host IP = 172. 29. 124. 97

Exercise 3:

What is the first valid host on the subnetwork that the node 172.30.15.74 255.255.240.0 belongs to?

Answer:

The first valid host IP = 172. 30. 0. 1

Exercise 4:

What is the first valid host on the subnetwork that the node 172.30.153.168/23 belongs to?

Answer:

The first valid host IP = 172. 30. 152. 1

Exercise 5:

What is the first valid host on the subnetwork that the node 172.30.181.215/23 belongs to?

Answer:

The first valid host IP = 172. 30. 180. 1

Exercise 6:

What is the first valid host on the subnetwork that the node 172.31.18.82/26 belongs to?

Answer:

The first valid host IP = 172. 31. 18. 65

Exercise 7:

What is the first valid host on the subnetwork that the node 192.168.242.135/27 belongs to?

Answer:

The first valid host IP = 192. 168. 224. 129

Exercise 8:

What is the first valid host on the subnetwork that the node 192.168.253.130/28 belongs to?

Answer:

The first valid host IP = 192. 168. 253. 129

See Also

Subnet Question Subnet Mask
Subnet Question Subnet Address