Prerequisites For Implementing Point To Point Layer 2 Services; Information About Implementing Point To Point Layer 2 Services; Layer 2 Virtual Private Network Overview; Layer 2 Local Switching Overview - Cisco ASR 9000 Series Configuration Manuallines

Implementing Point to Point Layer 2 Services

Prerequisites for Implementing Point to Point Layer 2 Services

You must be in a user group associated with a task group that includes the proper task IDs. The command
reference guides include the task IDs required for each command.
If you suspect user group assignment is preventing you from using a command, contact your AAA administrator
for assistance.

Information About Implementing Point to Point Layer 2 Services

To implement Point to Point Layer 2 Services, you should understand these concepts:

Layer 2 Virtual Private Network Overview

Layer 2 Virtual Private Network (L2VPN) emulates the behavior of a LAN across an L2 switched, IP or
MPLS-enabled IP network, allowing Ethernet devices to communicate with each other as they would when
connected to a common LAN segment. Point-to-point L2 connections are vital when creating L2VPNs.
As Internet service providers (ISPs) look to replace their Frame Relay or Asynchronous Transfer Mode (ATM)
infrastructures with an IP infrastructure, there is a need to provide standard methods of using an L2 switched,
IP or MPLS-enabled IP infrastructure. These methods provide a serviceable L2 interface to customers;
specifically, to provide virtual circuits between pairs of customer sites.
Building a L2VPN system requires coordination between the ISP and the customer. The ISP provides L2
connectivity; the customer builds a network using data link resources obtained from the ISP. In an L2VPN
service, the ISP does not require information about a the customer's network topology, policies, routing
information, point-to-point links, or network point-to-point links from other ISPs.
The ISP requires provider edge (PE) routers with these capabilities:
• Encapsulation of L2 protocol data units (PDU) into Layer 3 (L3) packets.
• Interconnection of any-to-any L2 transports.
• Emulation of L2 quality-of-service (QoS) over a packet switch network.
• Ease of configuration of the L2 service.
• Support for different types of tunneling mechanisms (MPLS, L2TPv3, IPSec, GRE, and others).
• L2VPN process databases include all information related to circuits and their connections.

Layer 2 Local Switching Overview

Local switching allows you to switch L2 data between two interfaces of the same type, (for example, Ethernet
to Ethernet) and on the same router. The interfaces can be on the same line card, or on two different line cards.
During these types of switching, Layer 2 address is used instead of the Layer 3 address. A local switching
connection switches L2 traffic from one attachment circuit (AC) to the other. The two ports configured in a
local switching connection are ACs with respect to that local connection. A local switching connection works
like a bridge domain that has only two bridge ports; traffic enters one port of the local connection and leaves
the other. However, because there is no bridging involved in a local connection, there is neither MAC learning
L2VPN and Ethernet Services Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.x
Prerequisites for Implementing Point to Point Layer 2 Services
75