Cisco VDSL config for ISP with RFC1483 bridging, DHCP and NAT

Telfort, a Dutch ISP, delivers VDSL connections using RFC1483 bridging. This is quite a different approach than the more common PPPoE setup. See below for an example.

First remove any ATM and Dialer interfaces you have defined, instead you use the Ethernet0 interface from the VDSL controller. Define a subinterface for the VLAN your ISP uses. In case of Telfort this is 34.

interface Ethernet0
no ip address
no shutdown
interface Ethernet0.34
encapsulation dot1Q 34
ip address dhcp
ip nat outside

On the subinterface you define that the IP address is requested through DHCP and with ip nat outside. Next apply the ip nat inside traffic on your internal interface, define your NAT rule and matching access list and you’re good to go. The default ip route is acquired via DHCP automatically.

interface Vlan1
ip address
ip nat inside
ip nat inside source list 101 interface Ethernet0.34 overload
access-list 101 permit ip any