Telenegar Knowledge Base

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====== Private vs Public IP Addresses ======

IP addresses are generally divided into two categories:

  * **Public IP Addresses**
  * **Private IP Addresses**

Understanding the difference is essential for troubleshooting network connectivity and interpreting the results of tools such as Telenegar IP Check.

-----

===== Public IP Addresses =====

A **public IP address** is globally unique and can be reached over the Internet.

Public IP addresses are assigned by Internet Service Providers (ISPs) and are routable across the global Internet.

Example:

<code>
8.8.8.8
1.1.1.1
93.184.216.34
</code>

When you visit a website, the website usually sees your **public IP address**.

-----

===== Private IP Addresses =====

A **private IP address** is used only inside a local network.

Private addresses are **not routed on the public Internet**.

The three private IPv4 ranges defined by RFC 1918 are:

^ Range ^ CIDR Prefix ^
| 10.0.0.0 – 10.255.255.255 | 10.0.0.0/8 |
| 172.16.0.0 – 172.31.255.255 | 172.16.0.0/12 |
| 192.168.0.0 – 192.168.255.255 | 192.168.0.0/16 |

Examples:

<code>
192.168.1.25
10.0.0.100
172.20.15.8
</code>

-----

===== Why Are Private Addresses Used? =====

Private addresses allow many devices to communicate within a local network without consuming globally unique public IPv4 addresses.

Typical devices using private addresses include:

  * Personal computers
  * Smartphones
  * Printers
  * Smart TVs
  * IP cameras
  * IoT devices

-----

===== How Do Private Devices Access the Internet? =====

Most home and office networks use a router that performs **Network Address Translation (NAT)**.

Example:

<code>
Laptop

192.168.1.25
       │
       ▼
Home Router
(NAT)
       │
       ▼
Public IP

203.0.113.25
       │
       ▼
Internet
</code>

External websites only see the router's public IP address.

-----

===== Can Two Devices Have the Same Private IP? =====

Yes.

Many different networks may use the same private addresses.

For example:

<code>
Home A

192.168.1.100

Home B

192.168.1.100
</code>

These devices do not conflict because they are on different private networks.

Public IP addresses, however, must be globally unique.

-----

===== Which IP Address Does a Website See? =====

Suppose your computer has:

<code>
Private IP

192.168.1.50
</code>

Your router has:

<code>
Public IP

198.51.100.25
</code>

When visiting a website:

<code>
Website

↓

198.51.100.25
</code>

The website does **not** see your private address.

-----

===== IPv6 =====

IPv6 has a similar concept.

Global addresses:

<code>
2001::/3
</code>

Unique Local Addresses (ULA):

<code>
fc00::/7
</code>

Unlike IPv4, IPv6 generally does not require NAT.

-----

===== How Can I Tell Whether an Address Is Private? =====

Examples:

^ Address ^ Type ^
| 8.8.8.8 | Public |
| 1.1.1.1 | Public |
| 192.168.1.20 | Private |
| 10.0.0.15 | Private |
| 172.20.5.9 | Private |
| 203.0.113.5 | Public (documentation example) |

-----

===== Private vs Public in Telenegar =====

Telenegar IP Check automatically determines whether an IP address is:

  * Public
  * Private
  * Loopback
  * Link-local
  * Reserved

This helps users quickly identify whether an address is expected to be reachable over the Internet.

-----

===== Common Misconceptions =====

  * **Private IP addresses are less secure than public IP addresses.**
    * False. "Private" refers to routing, not security.

  * **Every device connected to the Internet has its own public IPv4 address.**
    * False. Many devices share a single public address through NAT.

  * **A website can see my private IP address.**
    * False. It normally sees only your public IP address.

-----

===== Related Topics =====

  * [[networking:internet:ip-addresses|IP Addresses]]
  * [[networking:internet:ipv4|IPv4]]
  * [[networking:internet:ipv6|IPv6]]
  * [[networking:internet:nat|Network Address Translation (NAT)]]
  * [[networking:internet:loopback-addresses|Loopback Addresses]]
  * [[tools:ipcheck|IP Check]]

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{{tag>ip ipv4 ipv6 private-ip public-ip nat networking}}