Ho provato a confrontare la configurazione di questo post, ma con scarso successo: http://www.ciscoforums.it/viewtopic.php?t=9823
Lo strano è che se mi collego all'interfaccia LAN dell'857 e provo a pingare l'interfaccia WAN del router ovvero la punto-punto ricevo risposta, mentre se pingo il gateway della punto-punto no. ecco la mia configurazione:
Dati inventati (ovviamente

IP PUBBLICI: 10.0.0.232/29
IP PUNTO-PUNTO: 192.168.0.82
IP PUNTO-PUNTO GATEWAY: 192.168.0.1
!This is the running config of the router: 77.244.183.82
!----------------------------------------------------------------------------
!version 12.4
no service pad
service tcp-keepalives-in
service tcp-keepalives-out
service timestamps debug datetime msec localtime show-timezone
service timestamps log datetime msec localtime show-timezone
service password-encryption
service sequence-numbers
!
boot-start-marker
boot-end-marker
!
logging buffered 51200
logging console critical
enable secret 5 **********
!
no aaa new-model
clock timezone PCTime 1
clock summer-time PCTime date Mar 30 2003 2:00 Oct 26 2003 3:00
!
dot11 syslog
no ip source-route
!
!
ip cef
no ip bootp server
ip domain name yourdomain.com
ip name-server 217.22.224.51
ip name-server 217.22.224.52
!
!
!
username admin privilege 15 secret 5 *******
!
!
archive
log config
hidekeys
!
!
ip tcp synwait-time 10
ip ssh time-out 60
ip ssh authentication-retries 2
!
!
!
interface ATM0
no ip address
no ip redirects
no ip unreachables
no ip proxy-arp
ip route-cache flow
no atm ilmi-keepalive
dsl operating-mode auto
!
interface ATM0.1 point-to-point
description $FW_OUTSIDE$$ES_WAN$
ip address 192.168.0.82 255.255.255.0
ip virtual-reassembly
pvc 8/35
encapsulation aal5snap
!
!
interface FastEthernet0
!
interface FastEthernet1
!
interface FastEthernet2
!
interface FastEthernet3
!
interface Vlan1
description $ETH-SW-LAUNCH$$INTF-INFO-HWIC 4ESW$$ES_LAN$$FW_INSIDE$
ip address 10.0.0.233 255.255.255.248
no ip redirects
no ip unreachables
no ip proxy-arp
ip virtual-reassembly
ip route-cache flow
ip tcp adjust-mss 1452
!
ip forward-protocol nd
ip route 0.0.0.0 0.0.0.0 ATM0.1
!
ip http server
ip http access-class 23
ip http authentication local
ip http secure-server
ip http timeout-policy idle 60 life 86400 requests 10000
!
logging trap debugging
access-list 100 remark SDM_ACL Category=2
access-list 100 permit ip 10.0.0.233 0.0.0.7 any
no cdp run
!
control-plane
!
line con 0
login local
no modem enable
transport output telnet
line aux 0
login local
transport output telnet
line vty 0 4
privilege level 15
login local
transport input telnet ssh
!
scheduler max-task-time 5000
scheduler allocate 4000 1000
scheduler interval 500
sntp server 192.43.244.18
end