[c-nsp] L2TP DISCONNECT caused by LCP mismatch

[ahmad fadly]

Hi,

I'm currently setting up L2TP between LNS and PDSN,
when I dial to the PDSN the dial time sometimes takes
a long time to be connected. I debug ppp negotiation
and debug vpdn l2x-events, they show that the LCP
negotiation is having very long time negotiation but
sometimes is not. The message shows to be like this,
ppp807 LCP: Discarding: CP_CONFACK does not match
CP_CONFREQ. 

When LCP OPEN and PPP establishment has occured
finally L2TP is created. but sometimes after virtual
access goes up, the LCP renegotiates and cause the
virtual access goes down. 

I also have tried to dial with PPTP to this LNS with
the same virtual-template that L2TP used. And there is
no problem with LCP negotiation.

I think it because the LCP in this L2TP is unstable.
Does anyone know why the LCP is unstable? 

This is the topology:

PC----(PDSN-CDMA)---(L2TP)----LNS(7204VXR-NPE-G2)

The configuration :

!
vpdn-group 1
! Default L2TP VPDN group
 description End L2TP tunnel 
 accept-dialin
  protocol l2tp
  virtual-template 5
 local name LNS at IMM
 lcp renegotiation on-mismatch
 l2tp tunnel password 0 #######
 ip mtu adjust
!
vpdn-group pptp
! Default PPTP VPDN group
 accept-dialin
  protocol pptp
  virtual-template 5
 lcp renegotiation always
 ip mtu adjust

!
interface Virtual-Template5
 ip unnumbered Loopback100
 ip mtu 1420
 ip flow ingress
 ip tcp adjust-mss 1360
 no peer default ip address
 ppp mtu adaptive
 ppp authentication pap chap optional pradius
 ppp authorization pradius
 ppp ms-chap refuse
 ppp ms-chap-v2 refuse
 service-policy type control RULE5
!


aaa authentication login default local
aaa authentication ppp default group AAA
aaa authentication ppp pradius group AAA group BBB
aaa authorization config-commands
aaa authorization network default group AAA 
aaa authorization network pradius group AAA group BBB 
aaa authorization subscriber-service pradius group AAA
group BBB 

The Debug :

22:43:56: ppp807 PPP: Phase is ESTABLISHING
22:43:56: ppp807 PPP: Using vpn set call direction
22:43:56: ppp807 PPP: Treating connection as a callin
22:43:56: ppp807 PPP: Session handle[8E000155] Session
id[807]
22:43:56: ppp807 LCP: Event[OPEN] New State[Starting]
22:43:56: ppp807 PPP LCP: Enter passive mode,
state[Stopped]
22:43:57: ppp807 LCP: I CONFREQ [Stopped] id 6 len 14
22:43:57: ppp807 LCP:    ACCM 0x00000000
(0x020600000000)                             <<<<<< I
22:43:57: ppp807 LCP:    PFC (0x0702)
22:43:57: ppp807 LCP:    ACFC (0x0802)
22:43:57: ppp807 LCP: O CONFREQ [Stopped] id 1 len 14
22:43:57: ppp807 LCP:    AuthProto PAP (0x0304C023)
22:43:57: ppp807 LCP:    MagicNumber
0x08814572(0x050608814572)                <<<<<< II
22:43:57: ppp807 LCP: O CONFACK [Stopped] id 6 len 14
22:43:57: ppp807 LCP:    ACCM
0x00000000(0x020600000000)                            
 <<<<<< II
22:43:57: ppp807 LCP:    PFC (0x0702)
22:43:57: ppp807 LCP:    ACFC (0x0802)
22:43:57: ppp807 LCP: Event[Receive ConfReq+] New
State[ACKsent]
22:43:57: ppp807 LCP: I CONFACK [ACKsent] id 3 len 18
22:43:57: ppp807 LCP:    ACCM 0x00000000
(0x020600000000)                             <<<<<< I
22:43:57: ppp807 LCP:    AuthProto PAP (0x0304C023)   
                                            <<<<<< II
22:43:57: ppp807 LCP:    PFC (0x0702)
22:43:57: ppp807 LCP:    ACFC (0x0802)
##################
22:43:57: ppp807 LCP: Discarding: CP_CONFACK does not
match CP_CONFREQ     <<<<<< LCP Mismatch - I & II

##################
22:43:57: ppp807 LCP: I CONFACK [ACKsent] id 3 len 18
22:43:57: ppp807 LCP:    ACCM 0x00000000
(0x020600000000)
22:43:57: ppp807 LCP:    AuthProto PAP (0x0304C023)
22:43:57: ppp807 LCP:    PFC (0x0702)
22:43:57: ppp807 LCP:    ACFC (0x0802)
22:43:57: ppp807 LCP: Discarding: CP_CONFACK does not
match CP_CONFREQ
22:43:57: ppp807 LCP: I CONFACK [ACKsent] id 1 len 14
22:43:57: ppp807 LCP:    AuthProto PAP (0x0304C023)
22:43:57: ppp807 LCP:    MagicNumber 0x08814572
(0x050608814572)
22:43:57: ppp807 LCP: Event[Receive ConfAck] New
State[Open]
22:43:57: ppp807 LCP: I CONFACK [Open] id 1 len 14
22:43:57: ppp807 LCP:    AuthProto PAP (0x0304C023)   
                                             <<<<<<< 
II
22:43:57: ppp807 LCP:    MagicNumber 0x08814572
(0x050608814572)                <<<<<<<   II
22:43:57: ppp807 LCP: Discarding extra CONFACK
22:43:57: ppp807 LCP: Event[Receive ConfAck] New
State[Open]                                <<<<<<<  II
& II   Match
22:43:57: ppp807 PPP: Phase is AUTHENTICATING, by this
end
22:43:57: ppp807 LCP: State is Open

################

22:44:13: %LINEPROTO-5-UPDOWN: Line protocol on
Interface Virtual-Access3, changed state to up





Thanks a lot for every your comment and suggestion

IMM
Fadly