vpnc

vpnc is a command-line tool used in Linux and Unix systems for establishing a VPN (Virtual Private Network) connection. It is designed to connect to Cisco VPN concentrators and compatible devices.

The tool is primarily used to provide secure and encrypted network communication between the client computer and the VPN gateway. It supports various authentication methods, such as digital certificates, RSA SecurID, and preshared keys.

vpnc uses the IPSec protocol for creating a VPN tunnel and can work with both IPv4 and IPv6 networks. It also supports Network Address Translation Traversal (NAT-T) for establishing connections through NAT devices.

The configuration for vpnc is typically stored in a configuration file, where users can define settings such as the VPN server address, username, and password. Alternatively, these options can be specified through command-line arguments.

vpnc can be executed directly from the command line, and it also provides an interactive mode for configuring the VPN connection. Once connected, it allows users to access resources on the remote network securely.