vpnc

vpnc is a VPN client compatible with Cisco's VPN Concentrator (also known as EasyVPN equipment). It supports essential features for establishing connections including MD5 and SHA1 hashes, 3DES and AES ciphers, PFS, and various IKE DH group settings. The tool runs entirely in userspace and requires only the tun driver for network layer communication.

Use cases include connecting to corporate Cisco VPN gateways for secure remote access. It comes with helper tools like cisco-decrypt for decoding obfuscated pre-shared keys and pcf2vpnc for converting proprietary Cisco PCF config files to vpnc format.

Additional scripts such as vpnc-connect and vpnc-disconnect provide simplified connection management.

vpnc establishes IPSec VPN connections to Cisco 3000 Concentrators, IOS, and PIX devices using userspace implementation. It handles Xauth authentication, group secrets, and supports standard ciphers and hashes without kernel modules beyond tun. Helper tools process Cisco-specific configs: cisco-decrypt reverses obfuscation on pre-shared keys, while pcf2vpnc parses PCF files to generate vpnc-compatible configs.