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New Member

lcp negotiation failed

i need to configure win98 user dialer into 2511(access server).

i found i can't pass the lcp negotiation process.

my ios on 2511 is c2500-i-l.120-24.bin.

on debug message, I can see:

O CONFREQ ,

I CONFREQ,

O CONFACK,

and at last, the lcp process failed.

I need to know why? Why my router can't get I CONFACK? Is this one-way communication?

Thank you very much!

Sha

13 REPLIES
Bronze

Re: lcp negotiation failed

PPP consists of 3 phases:

- LCP

- Authentication

- NCP

Posting your config (just modify the addresses, names, passwords, phone numbers if you want) and the debug you have captured (debug for a single dial-up test is enough) should help.

Here are some info for the LCP phase:

PPP does not follow a client/server model. All connections are peer-to-peer. Therefore, when there is a caller and a receiver, both ends of the point-to-point connection must agree on the negotiated protocols and parameters.

When negotiation begins, each of the peers wanting to establish a PPP connection must send a Configure Request (seen in debug ppp negotiation and referred to hereafter as CONFREQ). Included in the CONFREQ are any options that are not the link default. These often include Maximum Receive Unit (MRU), Async Control Character Map (ACCM), Authentication Protocol (AuthProto), and the Magic Number. Also seen are the Maximum Receive Reconstructed Unit (MRRU) and Endpoint Discriminator (EndpointDisc), used for Multilink PPP.

There are three possible responses to any CONFREQ:

A Configure-Acknowledge (CONFACK) must be issued if the peer recognizes the options and agrees to the values seen in the CONFREQ.

A Configure-Reject (CONFREJ) must be sent if any of the options in the CONFREQ are not recognized (for instance, some vendor-specific options) or if the values for any of the options have been explicitly disallowed in the configuration of the peer.

A Configure-Negative-Acknowledge (CONFNAK) must be sent if all the options in the CONFREQ are recognized, but the values are not acceptable to the peer.

The two peers continue to exchange CONFREQs, CONFREJs and CONFNAKs until each sends a CONFACK, until the dial connection is broken, or until one or both of the peers indicates that the negotiation can not be completed.

Hope this helps.

New Member

Re: lcp negotiation failed

Sir,

Thank you!

Here is my router's configuration:

Router#sh run

Building configuration...

Current configuration:

!

version 12.0

service timestamps debug uptime

service timestamps log uptime

no service password-encryption

service udp-small-servers

service tcp-small-servers

!

hostname Router

!

enable password cisco2511

!

username jl password 7 151807

ip subnet-zero

!

interface Ethernet0

ip address 10.13.254.249 255.255.0.0

no ip directed-broadcast

!

interface Async9

ip unnumbered Ethernet0

no ip directed-broadcast

encapsulation ppp

keepalive 10

async mode dedicated

peer default ip address pool jl

no cdp enable

ppp authentication pap

!

ip local pool jl 10.13.2.1 10.13.2.20

ip classless

ip route 10.0.0.0 255.0.0.0 10.13.1.254

!

snmp-server community public RO

!

line con 0

transport input none

line 1 16

autoselect during-login

autoselect ppp

modem InOut

transport input all

speed 115200

flowcontrol hardware

line aux 0

transport input all

!

end

Router#

Here is my debug information:

"

3d18h: TTY9: DSR came up

3d18h: TTY9: destroy timer type 1

3d18h: TTY9: destroy timer type 0

3d18h: tty9: Modem: IDLE->READY

3d18h: %LINK-3-UPDOWN: Interface Async9, changed state to up

3d18h: As9 PPP: Treating connection as a dedicated line

3d18h: As9 PPP: Phase is ESTABLISHING, Active Open

3d18h: As9 LCP: O CONFREQ [Closed] id 111 len 24

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: AuthProto PAP (0x0304C023)

3d18h: As9 LCP: MagicNumber 0x23CEEFCE (0x050623CEEFCE)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: I CONFREQ [REQsent] id 2 len 23

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: MagicNumber 0x00A464C8 (0x050600A464C8)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: Callback 6 (0x0D0306)

3d18h: As9 LCP: O CONFREJ [REQsent] id 2 len 7

3d18h: As9 LCP: Callback 6 (0x0D0306)

3d18h: As9 LCP: TIMEout: State REQsent

3d18h: As9 LCP: O CONFREQ [REQsent] id 112 len 24

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: AuthProto PAP (0x0304C023)

3d18h: As9 LCP: MagicNumber 0x23CEEFCE (0x050623CEEFCE)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: I CONFREQ [REQsent] id 3 len 23

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: MagicNumber 0x00A464C8 (0x050600A464C8)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: Callback 6 (0x0D0306)

3d18h: As9 LCP: O CONFREJ [REQsent] id 3 len 7

3d18h: As9 LCP: Callback 6 (0x0D0306)

3d18h: As9 LCP: TIMEout: State REQsent

3d18h: As9 LCP: O CONFREQ [REQsent] id 113 len 24

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: AuthProto PAP (0x0304C023)

3d18h: As9 LCP: MagicNumber 0x23CEEFCE (0x050623CEEFCE)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: TIMEout: State REQsent

3d18h: As9 LCP: O CONFREQ [REQsent] id 114 len 24

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: AuthProto PAP (0x0304C023)

3d18h: As9 LCP: MagicNumber 0x23CEEFCE (0x050623CEEFCE)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: I CONFREQ [REQsent] id 4 len 23

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: MagicNumber 0x00A464C8 (0x050600A464C8)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: Callback 6 (0x0D0306)

3d18h: As9 LCP: O CONFREJ [REQsent] id 4 len 7

3d18h: As9 LCP: Callback 6 (0x0D0306)

3d18h: As9 LCP: TIMEout: State REQsent

3d18h: As9 LCP: O CONFREQ [REQsent] id 115 len 24

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: AuthProto PAP (0x0304C023)

3d18h: As9 LCP: MagicNumber 0x23CEEFCE (0x050623CEEFCE)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: I CONFREQ [REQsent] id 5 len 20

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: MagicNumber 0x00A464C8 (0x050600A464C8)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: O CONFACK [REQsent] id 5 len 20

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: MagicNumber 0x00A464C8 (0x050600A464C8)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: TIMEout: State ACKsent

3d18h: As9 LCP: O CONFREQ [ACKsent] id 116 len 24

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: AuthProto PAP (0x0304C023)

3d18h: As9 LCP: MagicNumber 0x23CEEFCE (0x050623CEEFCE)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: TIMEout: State ACKsent

3d18h: As9 LCP: O CONFREQ [ACKsent] id 117 len 24

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: AuthProto PAP (0x0304C023)

3d18h: As9 LCP: MagicNumber 0x23CEEFCE (0x050623CEEFCE)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: I CONFREQ [ACKsent] id 6 len 20

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: MagicNumber 0x00A464C8 (0x050600A464C8)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: O CONFACK [ACKsent] id 6 len 20

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: MagicNumber 0x00A464C8 (0x050600A464C8)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: TIMEout: State ACKsent

3d18h: As9 LCP: O CONFREQ [ACKsent] id 118 len 24

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: AuthProto PAP (0x0304C023)

3d18h: As9 LCP: MagicNumber 0x23CEEFCE (0x050623CEEFCE)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: I CONFREQ [ACKsent] id 7 len 20

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: MagicNumber 0x00A464C8 (0x050600A464C8)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: O CONFACK [ACKsent] id 7 len 20

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: MagicNumber 0x00A464C8 (0x050600A464C8)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: TIMEout: State ACKsent

3d18h: As9 LCP: O CONFREQ [ACKsent] id 119 len 24

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: AuthProto PAP (0x0304C023)

3d18h: As9 LCP: MagicNumber 0x23CEEFCE (0x050623CEEFCE)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: TIMEout: State ACKsent

3d18h: As9 LCP: O CONFREQ [ACKsent] id 120 len 24

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: AuthProto PAP (0x0304C023)

3d18h: As9 LCP: MagicNumber 0x23CEEFCE (0x050623CEEFCE)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: I CONFREQ [ACKsent] id 8 len 20

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: MagicNumber 0x00A464C8 (0x050600A464C8)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: O CONFACK [ACKsent] id 8 len 20

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: MagicNumber 0x00A464C8 (0x050600A464C8)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: TIMEout: State ACKsent

3d18h: As9 LCP: O CONFREQ [ACKsent] id 121 len 24

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: AuthProto PAP (0x0304C023)

3d18h: As9 LCP: MagicNumber 0x23CEEFCE (0x050623CEEFCE)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: I CONFREQ [ACKsent] id 9 len 20

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: MagicNumber 0x00A464C8 (0x050600A464C8)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: O CONFACK [ACKsent] id 9 len 20

3d18h: As9 LCP: ACCM 0x000A0000 (0x0206000A0000)

3d18h: As9 LCP: MagicNumber 0x00A464C8 (0x050600A464C8)

3d18h: As9 LCP: PFC (0x0702)

3d18h: As9 LCP: ACFC (0x0802)

3d18h: As9 LCP: TIMEout: State ACKsent

3d18h: TTY9: Async Int reset: Dropping DTR

3d18h: As9 LCP: State is Listen

3d18h: TTY9: DSR was dropped

3d18h: tty9: Modem: READY->HANGUP

3d18h: TTY9: dropping DTR, hanging up

3d18h: tty9: Modem: HANGUP->IDLE

3d18h: %LINK-5-CHANGED: Interface Async9, changed state to reset

3d18h: As9 LCP: State is Closed

3d18h: As9 PPP: Phase is DOWN

3d18h: TTY9: cleanup pending. Delaying DTR

3d18h: TTY9: cleanup pending. Delaying DTR

3d18h: TTY9: cleanup pending. Delaying DTR

3d18h: TTY9: destroy timer type 0

3d18h: TTY9: destroy timer type 1

3d18h: TTY9: destroy timer type 3

3d18h: TTY9: destroy timer type 4

3d18h: TTY9: destroy timer type 2

3d18h: Async9: allowing modem_process to continue hangup

3d18h: TTY9: restoring DTR

3d18h: %LINK-3-UPDOWN: Interface Async9, changed state to down

3d18h: As9 LCP: State is Closed

3d18h: As9 PPP: Phase is DOWN

"

Thanks again!

Regards,

Sha

Bronze

Re: lcp negotiation failed

From your debug, it seems that the router is rejecting LCP

3d18h: As9 LCP: O CONFREJ [REQsent] id 2 len 7

.

.

3d18h: As9 LCP: O CONFREJ [REQsent] id 3 len 7

.

.

3d18h: As9 LCP: O CONFREJ [REQsent] id 4 len 7

Try these options (one at a time):

1. Line config

line 1 16

stopbits 1

no speed 115200

modem autoconfigure discovery

2. Async interface config

interface Async9

async mode interactive

Also, you can enable "service timestamps debug datetime msec" and

"service timestamps log datetime msec" to include date and time

for debugs and logs.

Goodluck!

New Member

Re: lcp negotiation failed

Sir,

Is this the reject related with callback?

Thanks!

Sha

Bronze

Re: lcp negotiation failed

No. Callback feature is not enabled on your router based on the config.

The devices disagree on the MagicNumber.

The Magic number is a number generated locally that is sent to detect

a looped connection or an echo.

Magic number issues usually indicate that a loopback exists on the line.

Have you tried using the options?

New Member

Re: lcp negotiation failed

Sir,

No, I didn't do anything about magic number. I don't think i need to care this parameter. Why they can't meet the agreement about magic number?

And I found router rejected 3 times and then sent the CONFACK to PC. Should I increase the retry time of the LCP negotiation?

Thanks!

Regards,

Sha

Bronze

Re: lcp negotiation failed

As mentioned above, the MagicNumber is generated locally by the devices.

Sorry for that, I guess I didn't made it very clear.

When I said "Have you tried using the options?"

I meant the configs that I have posted.

These are also the configs used in some Cisco documents.

I have used these commands with Cisco 2511, 2509 and

other access servers and it works well.

As a guide, you are having problems on Layer 2 (Datalink),

so you can set aside first other troubleshooting procedures.

Also, I assume you have the correct settings on the dial-up client.

Goodluck.

New Member

Re: lcp negotiation failed

Sir,

Thank you first. I still have not took a testing. I will take a test later.

I want to discuss with you.

I think my modem is trained up as i can see the input packets. But why PC can't give me reply? PC got router's CONFREQ, it should give the router some response: CONFACK or CONFREJ. I just want to know Why pc ignore me?

How do you think my understanding? Is there something wrong?

Regards,

Sha

Bronze

Re: lcp negotiation failed

As you mentioned, there should be no problem with your modem,

but the negotiation should be both sides. Both sides should agree

on the parameters to be used for the datalink connection to succeed.

I think you're having a problem with the dial-up client settings.

You mentioned you are using Windows98-based PC to dial in to a 2511.

Please verify that you have the correct PC client settings including

Windows Dial-Up Networking (DUN) properties. Verify the:

PPP: Internet, Windows NT Server, Windows 98

as the type of dial-up server under the Server Type Tab

of the Internet Connection Icon.

You can also uncheck the NetBEUI and IPX/SPX checkbox.

One isolation you can do is to try dialing in to a different access

server (if you can) using the same PC and modem.

To tell you frankly, this troubleshooting could go a long way if

you won't be able to isolate the source of the problem. I don't have superb

knowledge about PPP but the suggestions I'm giving you are based on

actual, hands-on experience.

You can resolve this problem faster using a systematic method of troubleshooting.

I have some questions:

- What modem is connected to the 2511?

- What modem are you using for the dial-up client?

Thanks.

New Member

Re: lcp negotiation failed

Sir,

I've done configuration check on Win98 system. There is no problem. I will call out to another access server on this PC.

Ok, Thank you very very much for your advice in this case!

The device is remote to me. So the troubleshooting is a little difficult.

Thanks again. I will update the case when I get the answer.

Regards,

Sha

Bronze

Re: lcp negotiation failed

Hi Sha, just some info.

I'd like to make a correction with one of my replies.

I was confused with the exchange of LCP packets between

the router and the dial-up client.

You are right with the CONFREJ sent by the router to

the client because the client is the one requesting the

callback but the router rejected the option.

So the client should initiate another request without the

callback option. You can see in the debug that you have

posted, the client keeps on requesting the callback option.

It would be better if you can enable:

'service timestamps debug datetime msec'

so that we can see the correct pattern of responses from

router to the client and vice versa.

Once you have seen the message:

"LCP state is Open"

PPP LCP nego was completed successfully.

Goodluck!

Cisco Employee

Re: lcp negotiation failed

Configure the client not to request callback. After that you will not see CONFREJ during LCP negotiation.

Pay attention the following Rejacted parameters in CONFREJ

3d18h: As9 LCP: O CONFREJ [REQsent] id 2 len 7

3d18h: As9 LCP: Callback 6 (0x0D0306)

to know what is being rejected.

New Member

Re: lcp negotiation failed

Sir,

Thank you.

My PC run win98. It can't be configured with the callback parameter. I want to know why PC can't give the response to Router. Can you give me some points?

Thanks.

Sha

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