What is the subnet mask for a network that requires 30 usable IP addresses?

Practice Questions

Q1
What is the subnet mask for a network that requires 30 usable IP addresses?
  1. 255.255.255.224
  2. 255.255.255.240
  3. 255.255.255.192
  4. 255.255.255.248

Questions & Step-by-Step Solutions

What is the subnet mask for a network that requires 30 usable IP addresses?
  • Step 1: Understand that each subnet has a certain number of total IP addresses based on the subnet mask.
  • Step 2: Remember that the formula to calculate the number of usable IP addresses is 2^n - 2, where n is the number of bits available for hosts.
  • Step 3: Set up the equation: 2^n - 2 = 30 (for 30 usable addresses).
  • Step 4: Solve for n: 2^n = 30 + 2, which means 2^n = 32.
  • Step 5: Find n: Since 2^5 = 32, n = 5.
  • Step 6: Calculate the subnet mask: The total number of bits in an IP address is 32. If 5 bits are for hosts, then 32 - 5 = 27 bits are for the network.
  • Step 7: Write the subnet mask in CIDR notation: /27.
  • Step 8: Convert /27 to decimal format: The subnet mask is 255.255.255.224.
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