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Overview of IPv4 Classes

In the IPv4 IP address space, there are five classes: A, B, C, D and E. Each class has a specific range of IP addresses (and ultimately dictates the number of devices you can have on your network). Primarily, class A, B, and C are used by the majority of devices on the Internet. Class D and class E are for special uses.

The list below shows the five available IP classes, along with the number of networks each can support and the maximum number of hosts (devices) that can be on each of those networks. The four octets that make up an IPv4 address are conventionally represented by a.b.c.d - such as 127.10.20.30.

Additionally, information is also provided on private addresses and loop address (used for network troubleshooting).

It should be noted that the new IPv6 IP Standard is classless - it does not have different classes of IP addresses like the IPv4 standard. Thus, this article is strictly in reference to IPv4.

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IP Class & Mask Finder

Type any IPv4 address below to instantly see its class (A–E), whether it's public or private, and if it's a special range like loopback, link-local/APIPA, multicast, or reserved. We also show the historical "classful" default mask for learning - modern networks use CIDR - and you can jump to the full subnet calculator from the result.

IPv4 address:

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Class A Public & Private IP Address Range

Class A addresses are for networks with large number of total hosts. Class A allows for 126 networks by using the first octet for the network ID. The first bit in this octet, is always zero. The remaining seven bits in this octet complete the network ID. The 24 bits in the remaining three octets represent the hosts ID and allows for approximately 17 million hosts per network. Class A network number values begin at 1 and end at 127.

• Public IP Range: 1.0.0.0 to 126.255.255.255
  • First octet value range from 1 to 127
• Private IP Range: 10.0.0.0 to 10.255.255.255 (See Private IP Addresses below for more information)
• Special IP Range: 127.0.0.1 to 127.255.255.255 (See Special IP Addresses below for more information)
• Subnet Mask: 255.0.0.0 (8 bits)
• Number of Networks: 126
• Number of Hosts per Network: 16,777,214

Class A IP address ranges are typically used by Internet service providers and large corporations - such as Google and Apple.

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Class B Public & Private IP Address Range

Class B addresses are for medium to large sized networks. Class B allows for 16,384 networks by using the first two octets for the network ID. The first two bits in the first octet are always 1 0. The remaining six bits, together with the second octet, complete the network ID. The 16 bits in the third and fourth octet represent host ID and allows for approximately 65,000 hosts per network. Class B network number values begin at 128 and end at 191.

• Public IP Range: 128.0.0.0 to 191.255.255.255
  • First octet value range from 128 to 191
• Private IP Range: 172.16.0.0 to 172.31.255.255 (See Private IP Addresses below for more information)
• Subnet Mask: 255.255.0.0 (16 bits)
• Number of Networks: 16,382
• Number of Hosts per Network: 65,534

Class B IP address ranges are typically used by universities and medium-sized businesses.

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Class C Public & Private IP Address Range

Class C addresses are used in small local area networks (LANs). Class C allows for approximately 2 million networks by using the first three octets for the network ID. In a class C IP address, the first three bits of the first octet are always 1 1 0. And the remaining 21 bits of first three octets complete the network ID. The last octet (8 bits) represent the host ID and allows for 254 hosts per network. Class C network number values begins at 192 and end at 223.

• Public IP Range: 192.0.0.0 to 223.255.255.255
  • First octet value range from 192 to 223
• Private IP Range: 192.168.0.0 to 192.168.255.255 (See Private IP Addresses below for more information)
• Subnet Mask: 255.255.255.0 (24 bits)
• Number of Networks: 2,097,150
• Number of Hosts per Network: 254

Class C IP address ranges are typically used by small businesses and home networks.

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Class D IP Address Range

Class D IP addresses are not allocated to hosts and are used for multicasting. Multicasting allows a single host to send a single stream of data to thousands of hosts across the Internet at the same time. It is often used for audio and video streaming, such as IP-based cable TV networks. Another example is the delivery of real-time stock market data from one source to many brokerage companies.

• Range: 224.0.0.0 to 239.255.255.255
  • First octet value range from 224 to 239
• Number of Networks: N/A
• Number of Hosts per Network: Multicasting

Class D IP address ranges are typically used in multicast streaming services (e.g., video conferencing). Unlike Class A, B, and C, IPs in this class are not 'owned' by a specific entity. They are instead used temporarily and within an enterprise network for streaming content to multiple recipients simultaneously over their networks. For example, collaboration and streaming applications use Class D addresses for internal webinars or live video broadcast or a financial firm using it to deliver real-time stock market data to their customers.

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Class E IP Address Class

Class E IP addresses are not allocated to hosts and are not available for general use. These are reserved for research purposes.

• Range: 240.0.0.0 to 255.255.255.255
  • First octet value range from 240 to 255
• Number of Networks: N/A
• Number of Hosts per Network: Research/Reserved/Experimental

Class E IP address ranges are reserved and are not publicly used.

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Private IP Addresses

Within each network class, there are designated IP addresses that are reserved specifically for private/internal use only. These IP addresses cannot be used on Internet-facing devices as they are non-routable. For example, web servers and FTP servers must use non-private IP addresses. However, within your own home or business network, private IP addresses are assigned to your devices (such as workstations, printers, and home media server).

• Class A Private Range: 10.0.0.0 to 10.255.255.255
• Class B Private Range: 172.16.0.0 to 172.31.255.255
• Class C Private Range: 192.168.0.0 to 192.168.255.255
  

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Special IP Addresses (IPv4)

The following IPv4 addresses and blocks have special purposes. They are not globally routable on the public Internet and should not be used as ordinary host addresses. (Private RFC1918 ranges are listed in the "Private IP Addresses" section.)

Special-purpose IPv4 address blocks and their usage

Address / Block	Name	Purpose / Notes	Globally routable?
0.0.0.0	Unspecified address	"This host (unknown address)"; used as a source before a host gets an IP. Not assigned to interfaces. (Default route is 0.0.0.0/0 different concept.)	No
255.255.255.255	Limited broadcast	Broadcast to the local (layer-2) network only; routers must not forward.	No
127.0.0.0/8	Loopback	Host-internal traffic (e.g., 127.0.0.1); never leaves the device. These are virtual IP address, in that they cannot be assigned to a device. Specifically, the IP 127.0.0.1 is often used to troubleshoot network connectivity issues using the ping command. Specifically, it tests a computer's TCP/IP network software driver to ensure it is working properly. Learn how to use ping 127.0.0.1 to test your computer's TCP/IP network stack.	No (host-local only)
169.254.0.0/16	Link-local (APIPA)	Automatic Private IP Addressing (APIPA) is a feature with Microsoft Windows-based computers to automatically assign itself an IP address within this range when a Dynamic Host Configuration Protocol (DHCP) server is not available on the network. A DHCP server is a network device that is responsible for assigning IP addresses to devices on the network.	No (link-local only)
224.0.0.0/4	Multicast	Group addressing. 224.0.0.0/24 is local-subnet control; 239.0.0.0/8 is admin-scoped. Not unicast.	No (special multicast scope)
240.0.0.0/4	Reserved	Reserved for future use; commonly treated as invalid by hosts/routers.	No
100.64.0.0/10	CGNAT (Shared address space)	Used by ISPs for carrier-grade NAT; not the same as RFC1918 private space.	No (ISP-internal)
192.0.2.0/24, 198.51.100.0/24, 203.0.113.0/24	TEST-NET 1/2/3	Documentation and examples; safe to use in manuals, posts, and labs. Not used on the Internet.	No (documentation-only)
198.18.0.0/15	Benchmarking	Device and network interconnect testing/benchmarks (non-Internet use).	No (testing-only)

Tip: Private (RFC1918) ranges are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. They are not globally routable and should be NATed when accessing the Internet.

References: IANA Special-Purpose Address Registries; RFC 1918 (Private Use), RFC 3927 (Link-Local), RFC 6890 (Special-Purpose Address Registries).

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Summary of IPv4 Classes