Nortel BCM50e, Configuration

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228 Appendix E PPTP
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PPTP and the Business Secure Router
When the Business Secure Router is deployed in such a setup, it appears as a PC
to the ANT.
In Windows VPN or PPTP Pass-Through feature, the PPTP tunneling is created
from Windows 95, 98, and NT clients to an NT server in a remote location. Using
the pass-through feature, users on the network can access a different remote server
using the Business Secure Router's Internet connection. In SUA/NAT mode, the
Business Secure Router is able to pass the PPTP packets to the internal PPTP
server (for example, NT server) behind the NAT. You must configure port
forwarding for port 1723 to have the Business Secure Router forward PPTP
packets to the server. In the case above as the remote PPTP Client initializes the
PPTP connection, the user must configure the PPTP clients. The Business Secure
Router initializes the PPTP connection hence; there is no need to configure the
remote PPTP clients.
Figure 138 Business Secure Router as a PPTP client
PPTP protocol overview
PPTP is very similar to L2TP, since L2TP is based on both PPTP and L2F
(Cisco’s Layer 2 Forwarding). Conceptually, there are three parties in PPTP,
namely the PNS (PPTP Network Server), the PAC (PPTP Access Concentrator)
and the PPTP user. The PNS is the box that hosts both the PPP and the PPTP
stacks and forms one end of the PPTP tunnel. The PAC is the box that dials or
answers the phone calls and relays the PPP frames to the PNS. The PPTP user is
not necessarily a PPP client, it can also be a PPP server. Both the PNS and the
BCM50e Integrated Router