Network Class
Default Class Mask
Subnet Mask
IP Address
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DHCP Range
Broadcast Address
Total Addresses
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MAC Address formatter
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Summary of IPv4 Classes
| Class | Ranges | Subnet Mask | Notes | Number of Networks | Hosts per Network |
|---|---|---|---|---|---|
| A | Public 1.0.0.0 - 126.255.255.255Private 10.0.0.0 - 10.255.255.255Special 127.0.0.0 - 127.255.255.255localhost or loopback 127.0.0.1 |
255.0.0.0 |
0xxx First octet value 1-127 |
127 | 16,777,214 |
| B | Public 128.0.0.0 - 191.255.255.255Private 172.16.0.0 - 172.31.255.255 |
255.255.0.0 |
10xx First octet value 128-191 |
16,384 | 65,534 |
| C | Public 192.0.0.0 - 223.255.255.255Private 192.168.0.0 - 192.168.255.255 |
255.255.255.0 |
110x First octet value 192-223 |
2,097,152 | 254 |
| D | 224.0.0.0 - 239.255.255.255 |
1110 First octet value 224-239 |
N/A | Multicasting | |
| E | 240.0.0.0 - 255.255.255.255 |
1111 First octet value 240-255 |
N/A | Research, Reserved, Experimental |
Special IP Addresses (IPv4)
source: link
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.)
| 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).