• Chapter 1: Describing Network Requirements
• Chapter 2: Topologies for Teleworker Connectivity
• Chapter 3: Using Cable to Connect to a Central Site
• Chapter 4: Using DSL to Connect to a Central Site
• Chapter 5: Configuring DSL Access with PPPoE
• Chapter 6: Configuring DSL Access with PPPoA
• Chapter 7: DSL Connection Troubleshooting
• Chapter 8: The MPLS Conceptual Model
• Chapter 9: MPLS Architecture
• Chapter 10: Configuring Frame Mode MPLS
• Chapter 11: MPLS VPN Technologies
• Chapter 12: IPsec Overview
• Chapter 13: Site-to-Site VPN Operations
• Chapter 14: GRE Tunneling over IPsec
• Chapter 15: IPsec High Availability Options
• Chapter 16: Configuring Cisco Easy VPN
• Chapter 18: Cisco Device Hardening
• Chapter 19: Securing Administrative Access
• Chapter 20: Using AAA to Scale Access Control
• Chapter 21: Cisco IOS Threat Defense Features
• Chapter 22: Implementing Cisco IOS Firewalls
• Chapter 23: Implementing Cisco IDS and IPS

Chapter 6: Configuring DSL Access with PPPoA

PPPoA is defined in RFC 2364 as PPP over AAL5.

PPPoA Types

Three types of PPPoA are available:

• Virtual circuit multiplexed PPP over AAL5 (AAL5MUX) (RFC 2364)
• LLC encapsulated PPP over AAL5 (AAL5SNAP) (RFC 2364) (default)
• Cisco PPP over ATM (PPPoA) (Cisco proprietary)

VC-Multiplexed PPP over AAL5

Provides a separate virtual circuit for each routed protocol to be transported.

Configuration:

interface ATM0/0
 no ip address
 dsl operating-mode auto
 pvc 8/35
  encapsulation aal5mux ppp Virtual-Template1
!
interface Virtual-Template1
 encapsulation ppp
 ip address negotiated
 ppp authentication chap
 ...

LLC Encapsulated PPP over AAL5

Provides a single virtual circuit for all higher-layer protocols.

AAL5SNAP is the default method.

An LLC header is inserted at the beginning of the PDU.

The LLC header contains the following information:

• Destination Service Access Point (DSAP) - Set to 0xFE for SNAP
• Source Service Access Point (SSAP) - Set to 0xFE for SNAP
• Frame Type (Control) - 0x03 (unnumbered)

Configured with encapsulation aal5snap.

Cisco PPPoA

Allows for multiple PVCs on multiple subinterfaces.

Cisco equipment is required end-to-end.

Configured with encapsulation ciscoppp.