In the case studies that follow we will look into how L2TP can be setup in a couple of commonly utilized real life scenarios. While the first case study is a plain vanilla L2TP setup, the second one is more involved in that it uses IPsec to protect L2TP connections. This is a setup which has recently come into vogue for L2TP setups because of the need for a well managed encryption mechanism in L2TP. IPsec seems to fill these shoes well.
This case study shows a compulsory tunneling L2TP setup. In this scenario, the LAC is aware of L2TP and sets up a tunnel with the LNS. The client is unaware of the presence of L2TP and simply dials up to the LAC using PPP. Then it is tunneled over to the LNS.