In general virtual private networks (VPN) allows users to securely connect to private networks over the internet, acting as if they were directly connected to the network. There are two main types of VPNs, remote access and site-to-site.
Remote access VPNs allow clients to connect to a VPN server, giving the client access to a private network, allowing them to act as if they were directly connected to that private network.
The status of your remote access VPN can be viewed in the terminal, through the show command.
show vpn remote-access
Site-to-site VPNs connect two or more private networks, allowing them to interact with each other as if they were directly connected.
The status of your site-to-site VPN can be viewed in the terminal, again through the show command. Use autocomplete to view the different available commands. The following command shows all active IPsec Security Associations (which tunnels are up/down, and information about the connection).
show vpn ipsec sa
* For further details on anything in this part of the guide consult this pdf, which was used in creating this guide.