config vpnc in Ubuntu

$ sudo apt-get install vpnc

$ sudo vim /etc/vpnc/example.conf

IPSec gateway ***
IPSec ID ***
IPSec secret ***
Xauth username ***

gateway就是你要链接的地址 如：mobility.up.psu.edu(wireless) vpn.aset.psu.edu(wired)

ID就是Group name 如:pennstate(wireless) psuconnect(wired)

secret就是Group password 如:pennstate(wireless) psuconnect(wired)

Xauth username 即个人用户名

保存退出

$ sudo vpnc example.conf

输入密码 等待连接即可

Background Information:

virtual private network (VPN) virtual private network (VPN) is a communications network tunneled through another network, and dedicated for a specific network. One common application is secure communications through the public Internet, but a VPN need not have explicit security features, such as authentication or content encryption. VPNs, for example, can be used to separate the traffic of different user communities over an underlying network with strong security features.A VPN may have best-effort performance, or may have a defined Service Level Agreement (SLA) between the VPN customer and the VPN service provider. Generally, a VPN has a topology more complex than point-to-point. The distinguishing characteristic of VPNs are not security or performance, but that they overlay other network(s) to provide a certain functionality that is meaningful to a user community.

–from wikipedia vpnc is a open source client for Cisco VPN