Subnetting - How to determine the number of subnets and the number of hosts per
subnet?
Problem 1
IP Address 198.165.32.36/28
Answer the following questions by following all necessary steps.
Address class ________________________
The first/Network address ________________________
Custom subnet mask ________________________
Total number of subnets ________________________
Total number of host addresses ________________________
Number of usable addresses ________________________
Number of bits borrowed ________________________
What is the 2
nd subnet range? ______________________
What is the subnet number for the 5th subnet? ______________________
What is the subnet broadcast address for the 7th subnet? ______________________
Assignable addresses range for the 6th subnet? ______________________�
To determine the number of subnets and the number of hosts per subnet, we first need to identify the address class and calculate the number of bits borrowed for subnetting.
Step 1: Identify Address Class
The given IP address is 198.165.32.36/28. By looking at the first octet, we can identify that the address class is Class C.
Step 2: Calculate Number of Bits Borrowed
The subnet mask is given as /28. Since a Class C address already has a default subnet mask of /24, we need to borrow 4 bits for subnetting. The remaining 4 bits will be used for host addresses within each subnet.
Step 3: Calculate Number of Subnets
The formula to calculate the number of subnets is 2^n, where n is the number of borrowed bits. In this case, n = 4, so the number of subnets is 2^4 = 16.
Total number of subnets = 16
Step 4: Calculate Number of Host Addresses
The formula to calculate the number of host addresses per subnet is 2^n - 2, where n is the number of host bits. In this case, n = 4, so the number of host addresses per subnet is 2^4 - 2 = 14.
Total number of host addresses = 14
Step 5: Calculate Custom Subnet Mask
To calculate the custom subnet mask, we need to convert the borrowed bits to 1s and the remaining host bits to 0s. The default Class C subnet mask is 255.255.255.0, which has 24 network bits. Borrowing 4 bits will result in a custom subnet mask of 255.255.255.240.
Custom subnet mask = 255.255.255.240
Step 6: Calculate First/Network Address
To calculate the first/network address, we need to perform a bitwise AND operation between the IP address and the subnet mask.
Address: 198.165.32.36
Subnet Mask: 255.255.255.240
198.165.32.36 AND 255.255.255.240 = 198.165.32.32
First/Network Address = 198.165.32.32
Step 7: Calculate Number of Usable Addresses
The number of usable addresses is 2^n - 2, where n is the number of host bits. In this case, n = 4, so the number of usable addresses is 14.
Number of usable addresses = 14
Step 8: Calculate Number of Bits Borrowed
We already borrowed 4 bits for subnetting.
Number of bits borrowed = 4
Step 9: Calculate the 2nd Subnet Range
To calculate the 2nd subnet range, we need to calculate the network address and the broadcast address for the 2nd subnet.
Network Address: 198.165.32.32 (already calculated)
Broadcast Address: Network Address + Number of Usable Addresses - 1
Network Address: 198.165.32.32
Number of Usable Addresses: 14
Broadcast Address: 198.165.32.32 + 14 - 1 = 198.165.32.45
Second subnet range = 198.165.32.32 - 198.165.32.45
Step 10: Calculate Subnet Number for the 5th Subnet
To calculate the subnet number for the 5th subnet, we need to perform the following calculation:
Network Address + (Number of Usable Addresses * (Subnet Number - 1))
Network Address: 198.165.32.32 (already calculated)
Number of Usable Addresses: 14
Subnet Number: 5
198.165.32.32 + (14 * (5 - 1)) = 198.165.32.32 + 56 = 198.165.32.88
Subnet number for the 5th subnet = 198.165.32.88
Step 11: Calculate Subnet Broadcast Address for the 7th Subnet
To calculate the subnet broadcast address for the 7th subnet, we need to calculate the network address and the broadcast address for the 7th subnet.
Network Address: 198.165.32.32 (already calculated)
Broadcast Address: Network Address + Number of Usable Addresses - 1
Network Address: 198.165.32.32
Number of Usable Addresses: 14
Broadcast Address: 198.165.32.32 + 14 - 1 = 198.165.32.45
Seventh subnet broadcast address = 198.165.32.45
Step 12: Calculate Assignable Addresses Range for the 6th Subnet
To calculate the assignable addresses range for the 6th subnet, we need to calculate the network address and the broadcast address for the 6th subnet, excluding the network and broadcast addresses.
Network Address: Network Address + (Number of Usable Addresses * (Subnet Number - 1))
Broadcast Address: Network Address + (Number of Usable Addresses * Subnet Number) - 1
Network Address: 198.165.32.32 + (14 * (6 - 1)) = 198.165.32.32 + 70 = 198.165.32.102
Broadcast Address: 198.165.32.32 + (14 * 6) - 1 = 198.165.32.32 + 84 - 1 = 198.165.32.115
Assignable addresses range for the 6th subnet = 198.165.32.103 - 198.165.32.114
Address class: Class C
The first/Network address: 198.165.32.32
Custom subnet mask: 255.255.255.240
Total number of subnets: 16
Total number of host addresses: 14
Number of usable addresses: 14
Number of bits borrowed: 4
2nd subnet range: 198.165.32.32 - 198.165.32.45
Subnet number for the 5th subnet: 198.165.32.88
Subnet broadcast address for the 7th subnet: 198.165.32.45
Assignable addresses range for the 6th subnet: 198.165.32.103 - 198.165.32.114