Public and Private IPv4 Addresses (Free Preview)

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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 – /8 (
16 contiguous class B networks


20-bit block – /12 (
256 contiguous class C networks


16-bit block – /16 (

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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