Network Security Principles and Practices

Functional Details of L2TP

This section discusses the process through which L2TP is set up. Assuming the scenario in which the LAC and the client are separated from each other (compulsory tunneling), the L2TP setup starts with the client's initiating a PPP connection to the LAC. Upon receiving the connection request, the LAC does LCP negotiation with the client and challenges the client for authentication credentials. The client supplies these credentials such as a username, domain name, and password. The LAC uses the domain name to ascertain which LNS it needs to contact because it might be set up to work with multiple domains or different companies, each of which might have a separate LNS. This lookup can be done locally on the LAC or through ...