Type Of Address

Type Of Address

Example 1:
You are given the addressing information 10.10.8.0/22. What type of address is this?
Example 2:
You are given the addressing information 172.17.18.255/23. What type of address is this?
Example 3:
You are given the addressing information 192.168.25.130/25. What type of address is this?

Class A

Example 1:

You are given the addressing information 10.10.8.0/22. What type of address is this?

Solution:

Class A addresses use a default mask of 255.0.0.0
Given subnet mask = 255.255.252.0
Block Size = 256 – Subnet Mask
Valid subnets = 256 – 252 = 4, which means we have a block size
of 4 in the third octet.
Count by 4 until reaching 8.
Subnets are 0, 4, 8, 12 etc. 
Address 8 falls in the 8 subnet.
Subnet = 10. 10. 8. 0 
Next subnet address = 10. 10. 12. 0/22 
Broadcast address is 10. 10. 12. 255/22 of 10. 
10. 10. 8. 0/22 network. 
Valid host range = 10. 10. 8. 1 to 10. 10. 11. 254 
As the address 10.10.8.0/22 does not fall in the "10. 10. 8. 1 to
10. 10. 11. 254" range, so it is a subnet type address.

Class B

Example 2:

You are given the addressing information 172.17.18.255/23. What type of address is this?

Solution:

Class B addresses use a default mask of 255.255.0.0
Given subnet mask = 255.255.254.0
Block Size = 256 – Subnet Mask
Valid subnets = 256 – 254 = 2, which means we have a block size of
2 in the third octet.
Count by 2 until reaching 52.
Subnets are 0, 2, 4, … , 16, 18, 20 etc.
Address 18 falls in the 18 subnet.
Subnet = 172. 17. 18. 0
Next subnet address = 172. 17. 20. 0/23
Broadcast address is 172. 17. 19. 255/23 of 172.
172. 17. 18. 0/23 network.
Valid host range = 172. 17. 18. 1 to 172. 17. 19. 254
As the address 172.17.18.255/23 falls in the "172. 17. 18. 1 to
172. 17. 19. 254" range, so it is a host type address.

Class C

Example 3:

You are given the addressing information 192.168.25.130/25. What type of address is this?

Solution:

Class C addresses use a default mask of 255.255.255.0
Given subnet mask = 255.255.255.128
Block Size = 256 – Subnet Mask
Valid subnets = 256 – 128 = 128, which means we have a block size
of 128 in the forth octet.
Count by 128 until reaching 130.
Subnets are 0, 128, 256.
Address 130 falls in the 128 subnet.
Subnet = 192. 168. 25. 128
Next subnet address = 192. 168. 25. 256/25
Broadcast address is 192. 168. 25. 255/25 of 192. 168. 25. 128/25
network.
Valid host range = 192. 168. 25. 129 to 192. 168. 25. 254
As the address 192.168.25.130/25 falls in the "192. 168. 25. 129
to 192. 168. 25. 254" range, so it is a host type address.