ATM Configuration and Troubleshooting Guide

Configuring a Classical IP over ATM Interface over an ATM Interface
Summary of Classical IP over ATM
Chapter 326
Each node on the LAN reads the ARP request, and the node that “owns”
the IP address replies with a packet that contains its MAC address.
Figure 3-1 below shows this process.
Figure 3-1 Finding a Node’s MAC Address (IP Network)
IP over ATM Networks
Because ATM does not have the equivalent of a connectionless broadcast,
a mechanism is used to replace classic ARP and to find the ATM address
corresponding to an IP address.
A Logical IP Subnet (LIS) is a group of nodes that are on the same
subnet; that is, they can access each other without a router. One system
in the LIS is designated as the ATM ARP Server, and the rest are ATM
ARP Clients. Each ATM ARP Client is configured with the ATM address
of its ATM ARP Server. When the client boots, it contacts the server, and
they exchange information that allows the server to get the
IP-address-to-ATM-address mappings it needs. When a client wants to
use IP to connect to another system in the LIS, it sends an ATM ARP
request, containing the IP address of the destination, to the server. The
LAN
LAN
Node broadcasts
ARP request
containing IP address
of destination
Node that "owns" the
IP address replies
with its MAC address
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