Public and Private IPv4 Addresses (Preview)

Public IP addresses are IP addresses that are guaranteed to be globally unique to the internet. These addresses are globally routed between ISPs (Internet Service Providers).

Private Addresses

Private IPv4 addresses are defined in the RFC 1918.

Private IPv4 addresses cannot be routed on the internet.

They can be used by anyone on private networks, such as home and office networks, for internal communication.

These addresses are not guaranteed to be globally unique as other organizations and individuals can use the same private IPv4 address space.

 

The Internet Assigned Numbers Authority (IANA) has reserved the following three blocks of the IP address space for private networks:

 

Classful Description RFC 1918 Name Address Range Subnet Mask
Single class A network

 

24-bit block

 

10.0.0.0 – 10.255.255.255

 

10.0.0.0 /8 (255.0.0.0)
16 contiguous class B networks

 

20-bit block

 

172.16.0.0 – 172.31.255.255 172.16.0.0 /12 (255.240.0.0)
256 contiguous class C networks

 

16-bit block 192.168.0.0 – 192.168.255.255 192.168.0.0 /16 (255.255.0.0)

Figure Private IPv4 Addresses

 

Note: Only a portion of the “172” and the “192” address ranges are designated for private use. The remaining network addresses are “public” and routable on the global Internet.

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