Добрый день!
Ситуация следующая: настроил PPPoE сервер на 2811 (adventerprisek9.124-5a)(привожу конфиг):
!
vpdn enable
!
username pppoe password 0 <>
!
bba-group pppoe global
virtual-template 1
!
!
interface Loopback0
ip address 192.168.15.254 255.255.255.255
!
interface Virtual-Template1
ip unnumbered Loopback0
ip mtu 1492
peer default ip address pool PPPoE_pool
ppp authentication chap
!
ip local pool PPPoE_pool 192.168.59.20 192.168.59.30
!

Виндовые клиенты цепляются по PPPoE на сервер - проблем нет.

Пробую подцепиться на 1811 (advipservicesk9.124-2.XA)(привожу конфиг):
!
vpdn enable
!
bba-group pppoe global
sessions auto cleanup
!

interface FastEthernet0
ip address LAN_addr
duplex auto
speed auto
pppoe enable
pppoe-client dial-pool-number 1
!
!
interface Dialer1
ip address negotiated
ip mtu 1492
encapsulation ppp
dialer pool 1
no cdp enable
ppp authentication chap
ppp chap hostname pppoe
ppp chap password 0 <>
!

Вы спросите, а где же vpdn-group? Я его ввожу:
RTR#(config)#vpdn-group pppoe
RTR#(config-vpdn)#request-dial?
request-dialin  request-dialout

RTR#(config-vpdn)#request-dialin
RTR#(config-vpdn-req-in)#protocol ?
  l2f   Use L2F
  l2tp  Use L2TP
  pptp  Use PPTP

pppoe тут нет. Но, если вводить pppoe, то оно циска его принимает. А в sh run появляется bba-group pppoe global.

Дальше самое интересное: если включить debug ppp neg на pppoe-сервере, то видно, что клиент на Cisco 1811 пробует подцепиться на сервер, но проваливается 1 фаза PPP. Причем пароль/логин точно правильные.

Привожу debug:
*Mar 13 08:58:17.723: ppp721 PPP: Send Message[Dynamic Bind Response]
*Mar 13 08:58:17.723: ppp721 PPP: Using default call direction
*Mar 13 08:58:17.723: ppp721 PPP: Treating connection as a dedicated line
*Mar 13 08:58:17.723: ppp721 PPP: Session handle[FD000A4A] Session id[721]
*Mar 13 08:58:17.723: ppp721 PPP: Phase is ESTABLISHING, Active Open
*Mar 13 08:58:17.723: ppp721 LCP: O CONFREQ [Closed] id 1 len 19
*Mar 13 08:58:17.723: ppp721 LCP:    MRU 1492 (0x010405D4)
*Mar 13 08:58:17.723: ppp721 LCP:    AuthProto CHAP (0x0305C22305)
*Mar 13 08:58:17.723: ppp721 LCP:    MagicNumber 0x243DA6F2 (0x0506243DA6F2)
*Mar 13 08:58:19.719: ppp721 LCP: TIMEout: State REQsent
*Mar 13 08:58:19.719: ppp721 LCP: O CONFREQ [REQsent] id 2 len 19
*Mar 13 08:58:19.719: ppp721 LCP:    MRU 1492 (0x010405D4)
*Mar 13 08:58:19.719: ppp721 LCP:    AuthProto CHAP (0x0305C22305)
*Mar 13 08:58:19.719: ppp721 LCP:    MagicNumber 0x243DA6F2 (0x0506243DA6F2)
*Mar 13 08:58:19.719: ppp721 LCP: I CONFNAK [REQsent] id 2 len 8
*Mar 13 08:58:19.719: ppp721 LCP:    MRU 1500 (0x010405DC)
*Mar 13 08:58:19.719: ppp721 LCP: O CONFREQ [REQsent] id 3 len 19
*Mar 13 08:58:19.719: ppp721 LCP:    MRU 1500 (0x010405DC)
*Mar 13 08:58:19.719: ppp721 LCP:    AuthProto CHAP (0x0305C22305)
*Mar 13 08:58:19.719: ppp721 LCP:    MagicNumber 0x243DA6F2 (0x0506243DA6F2)
*Mar 13 08:58:19.719: ppp721 LCP: I CONFACK [REQsent] id 3 len 19
*Mar 13 08:58:19.719: ppp721 LCP:    MRU 1500 (0x010405DC)
*Mar 13 08:58:19.719: ppp721 LCP:    AuthProto CHAP (0x0305C22305)
*Mar 13 08:58:19.719: ppp721 LCP:    MagicNumber 0x243DA6F2 (0x0506243DA6F2)
*Mar 13 08:58:19.735: ppp721 LCP: I CONFREQ [ACKrcvd] id 2 len 15
*Mar 13 08:58:19.739: ppp721 LCP:    AuthProto CHAP (0x0305C22305)
*Mar 13 08:58:19.739: ppp721 LCP:    MagicNumber 0x3898153D (0x05063898153D)
*Mar 13 08:58:19.739: ppp721 LCP: O CONFACK [ACKrcvd] id 2 len 15
*Mar 13 08:58:19.739: ppp721 LCP:    AuthProto CHAP (0x0305C22305)
*Mar 13 08:58:19.739: ppp721 LCP:    MagicNumber 0x3898153D (0x05063898153D)
*Mar 13 08:58:19.739: ppp721 LCP: State is Open
*Mar 13 08:58:19.739: ppp721 PPP: Phase is AUTHENTICATING, by both
*Mar 13 08:58:19.739: ppp721 CHAP: O CHALLENGE id 1 len 29 from "2811"
*Mar 13 08:58:19.739: ppp721 CHAP: I CHALLENGE id 1 len 26 from "pppoe"
*Mar 13 08:58:19.739: ppp721 CHAP: I RESPONSE id 1 len 26 from "pppoe"
*Mar 13 08:58:19.739: ppp721 PPP: Phase is FORWARDING, Attempting Forward
*Mar 13 08:58:19.743: ppp721 PPP SSS: Receive SSS-Mgr Connect-Local
*Mar 13 08:58:19.743: ppp721 CHAP: Using hostname from unknown source
*Mar 13 08:58:19.743: ppp721 CHAP: Using password from AAA
*Mar 13 08:58:19.743: ppp721 CHAP: O RESPONSE id 1 len 29 from "2811"
*Mar 13 08:58:19.743: ppp721 PPP: Phase is AUTHENTICATING, Unauthenticated User
*Mar 13 08:58:19.743: ppp721 CHAP: I FAILURE id 1 len 25 msg is "Authentication failed"
*Mar 13 08:58:19.747: ppp721 LCP: I TERMREQ [Open] id 3 len 4
*Mar 13 08:58:19.747: ppp721 LCP: O TERMACK [Open] id 3 len 4
*Mar 13 08:58:19.747: ppp721 PPP: Sending Acct Event[Down] id[1A4E]
*Mar 13 08:58:19.747: ppp721 PPP: Phase is TERMINATING
*Mar 13 08:58:19.747: ppp721 PPP: Received Disconnect from Lower Layer
*Mar 13 08:58:19.747: ppp721 LCP: O TERMREQ [TERMsent] id 3 len 4
*Mar 13 08:58:19.747: ppp721 LCP: State is Closed
*Mar 13 08:58:19.747: ppp721 PPP: Phase is DOWN

В чем может быть проблема?