What is a subnet mask?

A subnet mask is a 32-bit number that divides an IP address into network and host portions. It determines which part of an IP address identifies the network and which part identifies the device.

What is CIDR notation?

CIDR (Classless Inter-Domain Routing) notation represents an IP address and its subnet mask using a slash followed by the number of network bits. For example, 192.168.1.0/24 means the first 24 bits are the network portion.

How do I calculate usable hosts?

Usable hosts = 2^(32 - CIDR) - 2. You subtract 2 because the first address is the network address and the last is the broadcast address, which cannot be assigned to hosts.

🌐 Subnet Calculator

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First Usable Host-

Last Usable Host-

Subnet Mask

Wildcard Mask

Total Hosts

Usable Hosts

CIDR Notation

IP Class

Binary Subnet Mask

IP Type

📚 CIDR Quick Reference

CIDR	Subnet Mask	Usable Hosts	CIDR	Subnet Mask	Usable Hosts
/24	255.255.255.0	254	/16	255.255.0.0	65,534
/25	255.255.255.128	126	/17	255.255.128.0	32,766
/26	255.255.255.192	62	/18	255.255.192.0	16,382
/27	255.255.255.224	30	/19	255.255.224.0	8,190
/28	255.255.255.240	14	/20	255.255.240.0	4,094
/29	255.255.255.248	6	/21	255.255.248.0	2,046
/30	255.255.255.252	2	/22	255.255.252.0	1,022

What is Subnetting?

Subnetting is the practice of dividing a network into smaller, more manageable sub-networks (subnets). This improves network performance, security, and IP address management.

The subnet mask determines which portion of an IP address identifies the network and which portion identifies the host. CIDR (Classless Inter-Domain Routing) notation uses a slash followed by the number of bits in the network portion.

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