D ebug vpdn event <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
*May 5 15:56:34.331: VPDN Received L2TUN socket message <xCRQ - Session Incoming>
*May 5 15:56:34.331: VPDN Tnl/Sn 18266 27 L2TUN socket session accept requested
*May 5 15:56:34.331: VPDN Tnl/Sn 18266 27 Setting up dataplane for L2-L2, no idb
*May 5 15:56:34.415: VPDN Received L2TUN socket message <xCCN - Session Connected>
*May 5 15:56:34.415: VPDN uid:30 VPDN session up
*May 5 15:56:34.435: VPDN uid:30 Virtual interface created for jerry.chen@cisco.com bandwidth 1544 Kbps
*May 5 15:56:34.439: VPDN Vi2.5 Virtual interface created for jerry.chen@cisco.com, bandwidth 1544 Kbps
*May 5 15:56:34.443: VPDN Vi2.5 Setting up dataplane for L2-L3, Vi2.5
R3#show
*May 5 15:56:34.475: VPDN Received L2TUN socket message <Dataplane UP>
当LNS收到LAC发过来的tunnel请求后，则接收这个请求，为L2-L2建立数据层面的通道，则会话建立，然后为这个用户生成一个虚拟接口vi2.5，继而建立L2到L3的数据层面的通道，然后数据通道形成.
debug vpdn protocol events
20:19:17: L2TP: I SCCRQ from DJ tnl 8
20:19:17: L2X: Never heard of DJ
20:19:17: Tnl 7 L2TP: New tunnel created for remote DJ, address 172.21.9.4
20:19:17: Tnl 7 L2TP: Got a challenge in SCCRQ, DJ
20:19:17: Tnl 7 L2TP: Tunnel state change from idle to wait-ctl-reply
20:19:17: Tnl 7 L2TP: Got a Challenge Response in SCCCN from DJ
20:19:17: Tnl 7 L2TP: Tunnel Authentication success
20:19:17: Tnl 7 L2TP: Tunnel state change from wait-ctl-reply to established
20:19:17: Tnl 7 L2TP: SM State established
20:19:17: Tnl/Cl 7/1 L2TP: Session FS enabled
20:19:17: Tnl/Cl 7/1 L2TP: Session state change from idle to wait-for-tunnel
20:19:17: Tnl/Cl 7/1 L2TP: New session created
20:19:17: Tnl/Cl 7/1 L2TP: O ICRP to DJ 8/1
20:19:17: Tnl/Cl 7/1 L2TP: Session state change from wait-for-tunnel to wait-connect
20:19:17: Tnl/Cl 7/1 L2TP: Session state change from wait-connect to established
20:19:17: Vi1 VPDN: Virtual interface created for kath@cisco.com
20:19:17: Vi1 VPDN: Set to Async interface
20:19:17: Vi1 VPDN: Clone from Vtemplate 1 filterPPP=0 blocking
20:19:18: %LINK-3-UPDOWN: Interface Virtual-Access1, changed state to up
20:19:18: Vi1 VPDN: Bind interface direction=2
20:19:18: Vi1 VPDN: PPP LCP accepting rcv CONFACK
20:19:19: %LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access1, changed
state to u p
Tnl 10 L2TP: Tunnel Authentication fails for partner------>> TUNNEL FAILURE
Tnl 10 L2TP: Tunnel state change from wait-ctl-reply to shutting-down
Tnl 10 L2TP: Shutdown tunnel
As7 10/1 L2TP: Destroying session
As7 10/1 L2TP: Session state change from wait-for-tunnel to idle10
Tnl 10 L2TP: Tunnel state shutting-down while destroying session
Tnl 10 L2TP: Tunnel state change from shutting-down to idle
Mar 1 01:04:32: %LINK-3-UPDOWN: Interface Async7, changed state to down
As7 VPDN: Reset
A77 VPDN: Cleanup
As7 VPDN: Reset
As7 VPDN: Unbind interface
%LINK-5-CHANGED: Interface Async7, changed state to reset
%LINK-3-UPDOWN: Interface Async7, changed state to down
当 tunnel 认证失败的时候， tunnel 就会从等待对方回应状态变为 down 状态，会话也会随之关闭，会话状态从等待 tunnel 建立状态变为 idle 状态，当会话失效以后， tunnel 又从 down 变为 idle ，随之内网接口变为 down 。
Router# show vpdn tunnel all
L2TP Tunnel Information (Total tunnels=1 sessions=1)
Tunnel id 2 is up, remote id is 10, 1 active session
Tunnel state is established, time since change: 00:32:28
Peer tunnel name is wander
Internet Address: 172.21.9.13, port 1701
Local tunnel name is stella
Internet Address: 172.21.9.4, port 1701
T unnel 两端必须配置本端用户名
Router# sh vpdn session all username kath@cisco.com
% No active L2TP tunnels
L2F Session
MID: 1
User: kath@cisco.com
Interface: Async6
State: open
Packets out: 139
Bytes out: 4518
Packets in: 422
Bytes in: 27013
用户名都要携带域名
首先是协商tunnel，然后会话建立，然后创建虚拟接入接口，然后PPP协商