Aqui está a configuração que usei e funcionou:
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname Router
!
boot-start-marker
boot-end-marker
!
logging message-counter syslog
!
no aaa new-model
!
!
dot11 syslog
ip source-route
no ip routing
!
no ip cef
no ipv6 cef
!
multilink bundle-name authenticated
!
archive
log config
hidekeys
!
interface ATM0
no ip address
no ip route-cache
no atm ilmi-keepalive
pvc 8/35
encapsulation aal5snap
!
bridge-group 1
!
interface FastEthernet0
!
interface FastEthernet1
!
interface FastEthernet2
!
interface FastEthernet3
!
interface Vlan1
no ip address
no ip route-cache
bridge-group 1
!
ip forward-protocol nd
no ip http server
no ip http secure-server
!
control-plane
!
bridge 1 protocol ieee
!
line con 0
no modem enable
line aux 0
line vty 0 4
login
!
scheduler max-task-time 5000
end
A fonte foi Guia de configuração e solução de problemas do Cisco DSL Router - Cisco DSL Router: PC como um PPPoE Client que precisava ser ajustado um pouco para o 877.