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4-2
Cisco Secure Router 520 Series Software Configuration Guide
OL-14210-01
Chapter 4 Configuring PPP over ATM with NAT
Configure the Dialer Interface
In this scenario, the small business or remote user on the Fast Ethernet LAN can connect to an Internet
service provider (ISP) using the following protocols on the WAN connection:
• Asymmetric digital subscriber line (ADSL) over plain old telephone service (POTS) using the
Cisco
Secure Router 520 ADSL-over-POTS routers
• ADSL over integrated services digital network (ISDN) using the Cisco Secure
Router
520 ADSL-over-ISDN routers
The Fast Ethernet interface carries the data packet through the LAN and off-loads it to the PPP
connection on the ATM interface. The ATM traffic is encapsulated and sent over the ADSL or ISDN
lines. The dialer interface is used to connect to the ISP.
PPPoA
The PPPoA Client feature on the router provides PPPoA client support on ATM interfaces. A dialer
interface must be used for cloning virtual access. Multiple PPPoA client sessions can be configured on
an ATM interface, but each session must use a separate dialer interface and a separate dialer pool.
A PPPoA session is initiated on the client side by the Cisco Secure Router 520 Series router.
NAT
NAT (represented as the dashed line at the edge of the Cisco router) signifies two addressing domains
and the inside source address. The source list defines how the packet travels through the network.
Configuration Tasks
Perform the following tasks to configure this network scenario:
• Configure the Dialer Interface
• Configure the ATM WAN Interface
• Configure DSL Signaling Protocol
• Configure Network Address Translation
An example showing the results of these configuration tasks is shown in the “Configuration Example”
section on page 4-9.
Configure the Dialer Interface
The dialer interface indicates how to handle traffic from the clients, including, for example, default
routing information, the encapsulation protocol, and the dialer pool to use. It is also used for cloning
virtual access. Multiple PPPoA client sessions can be configured on an ATM interface, but each session
must use a separate dialer interface and a separate dialer pool.