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IPサブネット計算

サブネットマスク、ネットワークアドレス、ブロードキャストを計算。

Network192.168.1.0
Broadcast192.168.1.255
Subnet Mask255.255.255.0
Wildcard0.0.0.255
First Host192.168.1.1
Last Host192.168.1.254
Hosts254
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How to Use

  1. Enter an IP address (e.g., 192.168.1.100)
  2. Enter the CIDR prefix length (e.g., /24) or subnet mask
  3. View the calculated network address, broadcast, and host range
  4. Copy any value you need for your network configuration

Common Use Cases

  • Planning IP address allocation for cloud VPCs
  • Configuring firewall rules with correct subnet ranges
  • Studying for network certification exams (CCNA, CompTIA)
  • Troubleshooting network connectivity issues

Frequently Asked Questions

What is CIDR notation?
CIDR (Classless Inter-Domain Routing) notation like /24 indicates how many bits are used for the network portion of an IP address. /24 means 24 network bits and 8 host bits, allowing 254 usable hosts.
How do I calculate the number of hosts in a subnet?
The formula is 2^(32-prefix) - 2 for IPv4. The subtraction accounts for the network address and broadcast address. A /24 subnet has 2^8 - 2 = 254 usable hosts.
What is the difference between network and broadcast address?
The network address is the first address in a subnet (all host bits 0) and identifies the subnet. The broadcast address is the last (all host bits 1) and sends packets to all hosts in the subnet.