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ADSL WAN Connections
PPPoA Overview
Creating the PPP Interface
To configure PPPoA, you configure the ADSL interface, the ATM interface,
and the ATM subinterface. (These instructions begin with “Configuring the
ADSL Interface: the Physical Layer” on page 7-12.) When configuring the ATM
subinterface, you must set the encapsulation to aal5snap or aal5mux ppp,
as shown below:
Syntax: encapsulation aal5snap
or
Syntax: encapsulation aal5mux [ip | ppp]
Your service provider should tell you which encapsulation to use.
The encapsulation setting configures the ATM adaptation layer (which is
called Layer 2-1). When you use PPPoA, you must also configure the ATM
point-to-point layer (which is called Layer 2-2). To configure this layer, you
create a PPP interface and then bind this interface to the ATM subinterface.
To create a PPP interface, move to the global configuration mode context
and enter:
Syntax: interface <interface> <number>
Replace <interface> with ppp and replace <number> with a number to
distinguish this PPP interface from other PPP interfaces on the router.
Assigning an IP Address
Because you are configuring a PPP interface on top of the ATM subinterface,
the PPP interface handles the IP address. Rather than configuring an IP
address on the ATM subinterface, you configure the IP address on the PPP
interface.
You can configure a static IP address, or you can configure the PPP interface
to negotiate an IP address from the service provider’s access concentrator.
To assign the PPP interface a static IP address, enter the following command
from the PPP interface configuration mode context:
Syntax: ip address <A.B.C.D> <subnet mask | /prefix length>
To configure the PPP interface to negotiate an IP address, enter:
Syntax: ip address negotiated
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