Topology: PC is of WIN-XP; R2631E is at VRP1.74-0105, serving as LNS of L2TP. PC gets an IP address of public network first, and then sets up an VPN tunnel of L2TP with R2631E directly.
Symptom: PC cannot dial into LNS.
L2TP::Chap response doesn''t pass authentication!
Modify the configurations of the router as follows: omit the authentication for tunnel, and PC could dial into R2631E.
! Default L2TP group
allow l2tp virtual-template 1
tunnel name LNS
undo tunnel authentication
///Disable authentication for L2TP tunnel
tunnel password simple 123456
When the router serves as LNS, it performs CHAP authentication for tunnel of L2TP by default. Also, PC does not authenticate the tunnel by default in dialing, but only PPP authentication for session. From the debugging information, we could know that CHAP authentication fails during establishing L2TP tunnel, resulting in the failure of PC to dial into LNS.