Configuration Guide for Preserve 802.1Q Tagging with 802.1P Marking over ATM PVCs

Quick guide from the manual

This document provides instructions for configuring the Preserve 802.1Q Tagging with 802.1P Marking over ATM PVCs feature. This feature allows 802.1Q tags to be transported over ATM permanent virtual circuits (PVC) used in ADSL2+ uplinks. It enables service providers to offer broadband-enabled services, such as voice, video, and data, with real-time network performance.

Prerequisites

• Basic understanding of ATM, bridging, DHCP, and VLANs.
• An ADSL2+ uplink.
• The feature is supported on Cisco IOS XE 17.x.

Restrictions

• Supports only one bridged 802.1Q VLAN.
• Can be configured only on a point-to-point ATM subinterface.
• Uses ATM Adaptation Layer 5 Subnetwork Protocol Access Protocol (AAL5SNAP) encapsulation.

Configuration steps

To configure the feature, follow these high-level CLI steps:

1. Enter privileged EXEC mode (enable) and global configuration mode (configure terminal).
2. Define class maps for egress and ingress traffic using class-map match-all.
3. Create policy maps using policy-map and define classes to set CoS values (set cos) and QoS groups (set qos-group).
4. Configure the ATM interface as point-to-point using interface atm.
5. Assign the interface to a bridge group (bridge-group).
6. Configure the PVC with pvc, bridge-dot1q encap, and encapsulation aal5snap.
7. Apply the service policies using service-policy out and service-policy input.
8. Configure PPPoE client settings if required using pppoe-client commands.

Troubleshooting

If you encounter issues with PPP session establishment, use the following debug commands:

• debug ppp authentication
• debug ppp negotiation

For RADIUS or TACACS server authentication issues, use:

• debug aaa authentication
• debug aaa authorization

Caution: Use debug commands with extreme caution as they are CPU-intensive and can impact network performance.

Technical concepts

The feature works by inserting an 802.1Q VLAN tag into the MAC Protocol Data Unit (PDU) before it is sent to the DSLAM. The bridge-dot1q encap command changes the local VLAN ID to the ID required by the service provider. Any 802.1P value is changed to 0, and frames without VLAN tags are sent out over ATM with an added VLAN header.