Virtual Private Networks, or VPNs, extend the reach of local-area networks without requiring owned or leased private lines. Businesses can use VPNs to give remote and mobile users network access, connect geographically separated branches into a unified network and enable the remote use of applications that rely on internal servers.

VPNs can use one or both of two mechanisms. One is to use private circuits leased from a trusted communications provider: alone, this is called a trusted VPN. The other is to send encrypted traffic over the public Internet: alone, this is called a secure VPN. Using a secure VPN over a trusted VPN is called a hybrid VPN. Combining two kinds of secure VPN into one gateway, for instance IPsec and SSL, is also called a hybrid VPN.

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