01-01: Exercises¶
Question¶
Find the address range, usable host range, network ID, and broadcast ID of the following subnet:
172.21.40.0/22
Solution¶
Method 1: Binary Method¶
Step 1: Write the Given IP Address in Binary¶
Subnet IP:
172.21.40.0 → 10101100.00010101.00101000.00000000
Subnet Mask:
/22 → first 22 bits are network bits, last 10 bits are host bits
Step 2: Determine the First and Last Address¶
- First address: keep all host bits as
0 - Last address: keep all host bits as
1
So,
-
First address:
10101100.00010101.00101000.00000000 → 172.21.40.0 -
Last address:
10101100.00010101.00101011.11111111 → 172.21.43.255
Step 3: Identify Network ID and Broadcast ID¶
- Network ID = first address = 172.21.40.0
- Broadcast ID = last address = 172.21.43.255
Step 4: Determine the Address Range¶
Address range:
172.21.40.0 to 172.21.43.255
Step 5: Determine the Usable Host Range¶
- First usable host: 172.21.40.1
- Last usable host: 172.21.43.254
Usable host range:
172.21.40.1 to 172.21.43.254
Method 2: Block Size Method¶
Step 1: Find the Subnet Mask and Block Size¶
Subnet Mask:
/22 → 11111111.11111111.11111100.00000000 → 255.255.252.0
Block size = 256 − 252 = 4
The block size applies in the 3rd octet.
Step 2: Find the Subnet Range¶
Subnets increase by 4 in the 3rd octet:
..., 36, 40, 44, ...
Given subnet:
172.21.40.0
So: - This subnet starts at 172.21.40.0 - The next subnet starts at 172.21.44.0
Therefore, the current subnet ends at:
172.21.43.255
Step 3: Identify Network ID and Broadcast ID¶
- Network ID = 172.21.40.0
- Broadcast ID = 172.21.43.255
Step 4: Determine the Address Range¶
Address range:
172.21.40.0 to 172.21.43.255
Step 5: Determine the Usable Host Range¶
- First usable host: 172.21.40.1
- Last usable host: 172.21.43.254
Usable host range:
172.21.40.1 to 172.21.43.254
Final Answer¶
- Network ID: 172.21.40.0
- Broadcast ID: 172.21.43.255
- Address range: 172.21.40.0 to 172.21.43.255
- Usable host range: 172.21.40.1 to 172.21.43.254