Panasonic NN46240-710 - Manual (Page 23)

Nortel Secure Router 8000 Series
Troubleshooting - VPN___________ 1 L2TP troubleshooting
1.1.2 L2TP tunnel session setup
Figure 1-2 shows the process for setting up an L2TP tunnel.
Figure 1-2 The process ^ow for setting up an L2TP tunnel
PC
9
LAC
RouterA
LAC
RADIUS Server
LNS
RouterB
LNS
RADIUS Server
(1) call setup
(2) PPP LCP setup
(3) PAP or CHAP
authentication
f
(4) access request
(5) access accept
(6) tunnel establish
(7) PAP or CHAP authentication
(challenge/response)
(8) authentication passes
(9) user CHAP response, PPP
negotiation parameter
(12) CHAP authentication twice(chaNenge/response)
(15) authentication passes
I
(10) access request
(11) access accept
(13) access request
(14) access accept
The procedure for setting up an L2TP tunnel is as follows:
1. The PC on the user side sends a connection request.
2. The PC and LAC device (Router A) negotiate the PPP LCP.
3. LAC carries out PAP or CHAP authentication based on the information from the PC.
4. LAC sends an access request with the VPN user name and password to the RADIUS
server for identity authentication.
5. The RADIUS server authenticates this user and sends an access accept message, such as
the LNS address. After the authentication succeeds, LAC is ready to start a new tunnel
request.
6. LAC makes a tunnel request to the LNS specified by the RADIUS server.
7. LAC informs LNS of a CHAP challenge, and LNS sends a CHAP response and its
CHAP challenge. LAC then sends back a CHAP response.
8. The authentication succeeds.
9. LAC transmits the information about the CHAP response, response identifier, and PPP
negotiation parameters to LNS.
Issue 5.3 (19 January 2009) Nortel Networks Inc. 1-3