ATM Configuration and Troubleshooting Guide

Configuring LAN Emulation Interfaces
Summary of LAN Emulation
Chapter 4 45
Multiprotocol Over ATM (MPOA)
Multiprotocol Over ATM (MPOA) provides high-performance, scalable
routing over switched ATM networks. To do this, MPOA establishes a
shortcut—a virtual circuit (VC) between two MPOA hosts in different
subnets—that bypasses any routers in between the two hosts. The pieces
of MPOA, and how they work together, are described below.
IMPORTANT HP’s implementation of ATM does not support MPOA for Token Ring
networks. This is because of a lack of MPOA Server (MPS) support for
Token Ring in routers.
Also, HP’s implementation does not support MPOA for secondary LANs.
The Pieces of MPOA
MPOA uses two protocols:
• LAN Emulation (LANE), Version 2—An enhanced version of LAN
Emulation, which provides Logical Link Control (LLC) Multiplexing
and support for the MPOA Client. LLC Multiplexing allows
multiple LECs and other protocols to share the same virtual circuits
(VCs). However, we recommend that you do not enable LLC
multiplexing, because it degrades performance.
• The Next Hop Resolution Protocol (NHRP)—Makes it possible for an
intermediate router’s packet-forwarding function to be bypassed.
NHRP is used to resolve the target address when the VC between
two MPOA hosts is being established.
MPOA has these logical components:
• MPOA Server (MPS)—Implements NHRP and resides on an MPOA
router. The MPS includes a Next Hop Server (NHS), and it works
with the NHS to resolve the Layer 3 target address of a shortcut
route for MPCs.
• MPOA Client (MPC)—Implements the client side of the MPOA
protocol. An MPC resides on a LAN Emulation Client (LEC) that is
an edge device or an MPOA host. An MPC’s main function is to be a
point of entry and exit for data flows that use shortcut routes. Note