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A VPN connects a PC, smartphone, or tablet to another computer (called a server) somewhere on the internet. But, i could comunicate to another pc even without a VPN, so what is the purpose of using it ?

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A VPN is a tunnel, usually encrypted, that connects two networks together as if they had a direct link between the two networks. Regardless of the number of hops it takes between the two networks, the tunnel looks like a single hop. The packets inside the tunnel are normally encrypted to maintain privacy (a company with two sites, or two companies, connected by a VPN over the public Internet want to keep proprietary information from falling into the wrong hands).

There are many reasons to use a tunnel. There are protocols that simply cannot be transported on the public Internet (multicast, routing protocols, etc.) that networks may need to share among themselves. Because the tunnel makes it look like a direct connection between the separated sites, and because the outer tunnel packets hide the inner packets, you can transport protocols across the Internet that cannot be transported by the Internet itself.

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  • What does it mean that the VPN is a "virtual private network" ? What is a private network in this context ?
    – AleWolf
    Nov 26 '19 at 16:17
  • The network link inside the tunnel is private. The Internet is a public network, and it has rules that must be followed, including things like addressing and routing. What goes on inside the tunnel is separate from the Internet. You can have private addressing and routing protocols other than BGP.
    – Ron Maupin
    Nov 26 '19 at 16:19
  • So it's like having a long ethernet cable that connects the devices ?
    – AleWolf
    Nov 26 '19 at 16:20
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    That depends on the PC and its configuration. Unfortunately, host/server questions are off-topic here. It is certainly possible that a PC can be configured to bridge or route traffic between interfaces (a tunnel interface on a PC is just another interface, like an ethernet interface). You can ask about configuring your PC on Super User.
    – Ron Maupin
    Nov 26 '19 at 16:24
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    That is really too broad. We would need more context, but if you mean as interface on a host, then yes, an interface is an interface.
    – Ron Maupin
    Nov 26 '19 at 16:26
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A VPN link mainly serves two purposes:

  • transparent routing: the tunnel allows each side to transparently use the other side's addressing scheme (usually: private IP address space connect over public IP address space); since the source addresses may remain original, they can be used for security/trust
  • encryption: traffic is completely encrypted; an eavesdropper can merely detect that there's traffic, but he can't get at the data and can't even see who is talking to whom (metadata), regardless of whether end-to-end encryption is used or not
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VPN stand for Virtual Private network. It makes secured tunnel through public internet. Generally we don't use VPN in Local area network and if you want to connect with your branch network in separate location, then best and secured solution will be VPN.

wikipedia Says

A virtual private network extends a private network across a public network, and enables users to send and receive data across shared or public networks as if their computing devices were directly connected to the private network.

There are two major type of VPNs.

  • Site to site VPN
  • Remote Site vpn

Especially VPN are secured because It transfer encrypted traffic. Based technically you can find many VPNs such as SSL,IPSec, Flex and many more....

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