How the VPN Client Works

How the VPN Client Works

The VPN Client works with a Cisco VPN server to create a secure connection, called a tunnel, between 

your computer and the private network. It uses the Internet Key Exchange (IKE) and Internet Protocol 

Security (IPSec) tunneling protocols to make and manage secure connections. Some of the steps include:

• Negotiating tunnel parameters—Addresses, algorithms, lifetime, and so on.

• Establishing tunnels according to the parameters.

• Authenticating users—Making sure users are who they say they are, by usernames, group names and 

passwords, and X.509 digital certificates.

• Establishing user access rights—Hours of access, connection time, allowed destinations, allowed 

protocols, and so on.

• Managing security keys for encryption and decryption.

• Authenticating, encrypting, and decrypting data through the tunnel.

For example, to use a remote PC to read e-mail at your organization, you connect to the Internet, then 

start the VPN Client and establish a secure connection through the Internet to your organization's private 

network. When you open your e-mail, the Cisco VPN server uses IPSec to encrypt the e-mail message. 

It then transmits the message through the tunnel to your VPN Client, which decrypts the message so you 

can read it on your remote PC. If you reply to the e-mail message, the VPN Client uses IPSec to process 

and return the message to the private network through the Cisco VPN server.

How the VPN Client Works

How the VPN Client Works

The VPN Client works with a Cisco VPN server to create a secure connection, called a tunnel, between 

your computer and the private network. It uses the Internet Key Exchange (IKE) and Internet Protocol 

Security (IPSec) tunneling protocols to make and manage secure connections. Some of the steps include:

• Negotiating tunnel parameters—Addresses, algorithms, lifetime, and so on.

• Establishing tunnels according to the parameters.

• Authenticating users—Making sure users are who they say they are, by usernames, group names and 

passwords, and X.509 digital certificates.

• Establishing user access rights—Hours of access, connection time, allowed destinations, allowed 

protocols, and so on.

• Managing security keys for encryption and decryption.

• Authenticating, encrypting, and decrypting data through the tunnel.

For example, to use a remote PC to read e-mail at your organization, you connect to the Internet, then 

start the VPN Client and establish a secure connection through the Internet to your organization's private 

network. When you open your e-mail, the Cisco VPN server uses IPSec to encrypt the e-mail message. 

It then transmits the message through the tunnel to your VPN Client, which decrypts the message so you 

can read it on your remote PC. If you reply to the e-mail message, the VPN Client uses IPSec to process 

and return the message to the private network through the Cisco VPN server.