CIDR and Subnet Calculator
Enter an IPv4 address with a prefix such as 192.168.1.10/24, or an address and a subnet mask. See the network address, broadcast address, masks and the usable range.
このコンテンツは英語です。
計算例
A home network
192.168.1.10/24
Network address: 192.168.1.0 Subnet mask: 255.255.255.0 Wildcard mask: 0.0.0.255 Broadcast address: 192.168.1.255 First usable address: 192.168.1.1 Last usable address: 192.168.1.254 Total addresses: 256 Usable addresses: 254 Prefix length: /24 Address type: Local network range
A /24 holds 256 addresses and 254 can be used.
An address and a mask
10.0.0.5 255.255.255.252
Network address: 10.0.0.4 Subnet mask: 255.255.255.252 Wildcard mask: 0.0.0.3 Broadcast address: 10.0.0.7 First usable address: 10.0.0.5 Last usable address: 10.0.0.6 Total addresses: 4 Usable addresses: 2 Prefix length: /30 Address type: Local network range
The mask is the same as /30, which holds four addresses.
CIDR and Subnet Calculator について
This calculator works out the details of an IPv4 subnet. Enter an address with a prefix, such as 192.168.1.10/24, or an address and a subnet mask, and you get the network address, the broadcast address, both masks and the range of usable addresses.
It also shows how many addresses the block holds, how many can be given to hosts, and whether the range is for a local network, public, loopback or something else. It covers IPv4 only.
CIDR and Subnet Calculator の使い方
- Type an address with a prefix length, or an address and a subnet mask.
- Read the network, broadcast and usable range.
- Change the prefix to see how the block grows or shrinks.
主な使いみち
- Planning how to split a network into subnets
- Checking the usable range for a router or firewall rule
- Finding the broadcast address of a subnet
- Converting between a prefix and a subnet mask
よくあるご質問
What does /24 mean?
The first 24 of the 32 bits identify the network, which leaves 8 bits for hosts. That is a subnet mask of 255.255.255.0 and a block of 256 addresses.
Why are two addresses not usable?
The first address in a block names the network and the last is the broadcast address, so a /24 has 254 usable addresses. A /31 is a special case with two usable addresses and a /32 is a single address.
What is the wildcard mask?
The subnet mask turned inside out. A mask of 255.255.255.0 gives a wildcard of 0.0.0.255. Some router rules use it.
Does it work with IPv6?
No. This calculator is for IPv4 addresses.