IPv4 Subnet 計算機
「IPv4 Subnet 計算機」はコード、データと QRに使えるブラウザツールです。入力内容と結果は通常この端末内で処理され、登録は必要ありません。
使い方
使い方
- Enter an IPv4 address and choose a CIDR prefix length.
- Calculate the network and review the mask, broadcast, range, and host count.
- Copy the results into a network plan or configuration.
CIDR subnet boundaries
The calculator applies the selected prefix bit by bit to find the network address, then derives the broadcast address from the remaining host bits.
Host counts include edge cases
Traditional subnets exclude network and broadcast addresses. /31 is reported as a two-address point-to-point subnet, and /32 contains one address.
Local browser processing
Validation and calculation happen in your browser. The address is not sent to a server and no network request is made.
よくある質問
あわせて知りたいこと
What does /24 mean?
It means 24 of the 32 IPv4 bits identify the network, leaving 8 bits for addresses inside it.
Why are there 254 usable hosts in a /24?
A /24 has 256 total addresses; the network and broadcast addresses are normally reserved, leaving 254 host addresses.
Does this check whether the subnet is in use?
No. It only performs local arithmetic and does not scan, ping, or query any network.
What are /31 and /32 used for?
/31 commonly represents a point-to-point link with two usable endpoints. /32 represents one exact IPv4 address.