Cisco CISCO876-SEC-I-K9 Configuration Guide - Page 48

Chapter 4 Configuring PPP over ATM with NAT 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 857 or Cisco 877 router • ADSL over integrated services digital network (ISDN) using the Cisco 876 router • Single-pair high-speed digital subscriber line (G.SHDSL) using the Cisco 878 router 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, ISDN, or G.SHDSL 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 850 or Cisco 870 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 4-11. Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide 4-2 OL-5332-01