This process is completely transparent to your network and applications. Authentication - For Secure Connection Authentication is the most important security element of a multiprotocol IP tunnel. Authentication ensures that tunnels will only be established between verified tunnel partners. Different tunneling protocols approach the issue of authentication in different ways. Tunnel authentication is based on digital signature technology, using the MD5 standard.
Authentication occurs before the connection is established.
Once the connection has been established, however, there is no further authentication of packets. Make sure you know what kind of authentication is provided with any VPN product you consider. The Cisco 3XXX and 5XXX concentrators establish secure tunnels using the IETF IPSec standard. IPSec operates at Layer 3 of the OSI model. This means that the VPN concentrator produces straight IP packets that are compatible with every ISP and every IP router in the world.