PPPoE And 2811 Router - Bridged mode

Unanswered Question
Aug 25th, 2008

Hi, I am trying to get a cellular router working in bridged mode so I can set up a VPN tunnel from a Cisco router. I am not able to get the PPPoE connection established and was hoping someone could help. My config is: Internet-->Cellular780seu-->(FA0/0)2821(FA0/1)


vpdn enable


interface FastEthernet0/0

no ip address

no ip mroute-cache

duplex auto

speed auto

pppoe enable group global

pppoe-client dial-pool-number 1

no cdp enable


interface FastEthernet0/1

ip address

ip nat inside

ip virtual-reassembly

duplex auto

speed auto


interface Dialer1

description Logical ADSL Interface

ip address negotiated

ip mtu 1492

ip nat outside

ip virtual-reassembly

encapsulation ppp

ip tcp adjust-mss 1452

no ip mroute-cache

dialer pool 1

dialer-group 1

no cdp enable

ppp authentication pap

ppp ipcp route default


ip route FastEthernet0/0


ip http server

no ip http secure-server

ip nat inside source list 10 interface Dialer1 overload


access-list 10 permit

dialer-list 1 protocol ip permit

no cdp run


This connection does not require a username & password, and works when I set up a miniport dial using WinXP. Can someone please assist?


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Giuseppe Larosa Mon, 08/25/2008 - 01:18

Hello Mattie,

>> This connection does not require a username & password

then remove ppp authentication pap

inside dialer interface config

you can use debug ppp neg and debug ppp auth to see what happens

Hope to help


mattiep00 Mon, 08/25/2008 - 01:51

Thanks for the quick response. I have removed the auth, but nothing is happening after shutting/nos hutting the interface. I have the following ints:

FA0/0 unassigned UP UP


NVI0 unassigned UP UP

Virtual-Access1 UP UP

Virtual-Access2 DOWN DOWN

DAILER1 unassigned UP UP

Debugs are not showing anything. I have tried pinging from the interface to google's IP address with no activity...

Giuseppe Larosa Mon, 08/25/2008 - 04:19

Hello Matt,

now we need to understand when the PPPoE session fails:




show pppoe session

debug pppoe {data | errors | events | packets}

note: depending on IOS release config of PPPoE release requires or doesn't require the vpdn configuration.

If you need vpdn :

vpdn enable

vpdn-group 1


protocol pppoe


after release 12.2(13)T config changes

Hope to help


mattiep00 Mon, 08/25/2008 - 20:34

Ok, getting a bit closer. When i now do a debug ppp negotiation i get the attached. Interfaces go up, then come back down. Any ideas?

Giuseppe Larosa Mon, 08/25/2008 - 22:29

Hello Matt,

I see that you still have some authentication issue:

in the first log file I see:

*Aug 25 22:38:40.355: Vi2 PPP: No authorization without authentication

*Aug 25 22:38:40.355: Vi2 PPP: Phase is AUTHENTICATING, by the peer

*Aug 25 22:38:40.363: Vi2 CHAP: I CHALLENGE id 1 len 35 from "UMTS_CHAP_SRVR"

*Aug 25 22:38:40.363: Vi2 CHAP: Unable to authenticate for peer

*Aug 25 22:38:40.363: Vi2 PPP: Sending Acct Event[Down] id[4A]

*Aug 25 22:38:40.363: Vi2 PPP: Phase is TERMINATING

your router is receveing a CHAP challenge from the PPP peer UMTS_CHAP_SRVR

in the second log file I see a change: now there is a mismatch on the authentication protocol between CHAP :

Aug 26 04:03:49.106: Vi2 LCP: AuthProto CHAP (0x0305C22305)

and MS-CHAP (that is different)

it looks like your router is proposing MS-CHAP and the peer rejects it

Try to use CHAP on your router.

*Aug 26 04:03:49.142: Vi2 LCP: O CONFREQ [ACKsent] id 5 len 15

*Aug 26 04:03:49.142: Vi2 LCP: AuthProto MS-CHAP (0x0305C22380)

*Aug 26 04:03:49.142: Vi2 LCP: MagicNumber 0x1CB58CB2 (0x05061CB58CB2)

*Aug 26 04:03:49.158: Vi2 LCP: I CONFREJ [ACKsent] id 5 len 9

*Aug 26 04:03:49.158: Vi2 LCP: AuthProto MS-CHAP (0x0305C22380)

Your router sends a Config request with auth proto = MS-CHAP the other side answers with a config reject for this protocol.

Try to use CHAP on the router instead of MS-CHAP.

Hope to help



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