Huawei AR1200 series Configuration Manual page 260

Huawei AR1200 Series Enterprise Routers
Configuration Guide - VPN
Figure 4-3 Networking diagram of call setup in an L2TP tunnel
The following steps describe the call setup process in an L2TP tunnel:
1.
2.
3.
4.
5.
6.
7.
8.
Issue 01 (2012-04-20)
LAC
PC
RouterA
(1) call setup
(2) PPP LCP setup
(3) PAP or CHAP
authentication
(4) access request
(5) access accept
(12) CHAP authentication twice(challenge/response)
(15) authentication passes
A PC initiates a call-connecting request.
The PC and RouterA (LAC) negotiate PPP LCP parameters.
RouterA performs Password Authentication Protocol (PAP) or Challenge Handshake
Authentication Protocol (CHAP) authentication on the user information provided by the
PC.
RouterA sends an access request, which contains the user's name and password, to the LAC
RADIUS server for identity authentication.
The LAC RADIUS server authenticates this user and replies with an access-accepting
message, such as the LNS address corresponding to the user. After authentication is
successful, RouterA prepares to initiate a tunnel request.
RouterA initiates a tunnel request to the RouterB (LNS) specified by the LAC RADIUS
server.
RouterA informs RouterB of a CHAP challenge, and RouterB replies with a CHAP
response and its CHAP challenge. The RouterA then replies with a CHAP response.
Authentication is performed successfully.
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LAC
RADIUS
Server
(6) tunnel establish
(7) PAP or CHAP authentication
(challenge/response)
(8) authentication passes
(9) user CHAP response,
PPP negotiation parameter
4 L2TP Configuration
LNS
RouterB
(10) access request
(11) access accept
(13) access request
(14) access accept
LNS
RADIUS
Server
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