Troubleshooting guide

13-7
ATM and Layer 3 Switch Router Troubleshooting Guide
OL-1969-01
Chapter 13 Troubleshooting ATM Router Module Connections
Hardware and Software Restrictions of the ATM Router Module
Note The ATM router module is only supported on ATM switches that have a multiservice ATM switch
processor installed.
Understanding Packet and Cell Flow
This section describes packet flow through the ATM router module.
An ATM router module interface does not have any capabilities for ATM signalling. All ATM signaling
is directed to the main route processor. The route processor is also responsible for setting up all ATM
related VCs to enable the ATM router module to route any data traffic that it processes.
The ATM router module provides a packet-parsing, or look-up, engine that does not exist on the other
ATM port adapter modules in the switch router. Data traffic coming from an ATM cloud targeted to hosts
on the Ethernet side of the switch router are terminated on the ATM router module. The ATM router
module processes the packets to identify the target port before the packets are sent to the Ethernet ports,
ATM port, or route processor.
Note All LANE control frames are sent to route processor.
When an ATM router module encounters a spanning tree packet or an ARP request, it passes it to the
route processor. Unlike an Ethernet module, the packet may have LANE or RFC 1483 encapsulation,
and the packet must be transferred to the respective protocol layer once it reaches the route processor.
For this to happen, one data VC per protocol is created when the ATM router module is initialized. These
VCs are enabled as long as the ATM router module is present in the system.
The ATM router module port needs no external interfaces, such as cables, to come up. Each ATM router
module interface has a unique MAC Address which is allocated by the route processor. You can
configure subinterfaces on the ATM router module interfaces where the LECS or RFC 1483 clients are
configured. The ATM interface allows limited ATM functionality; the subinterfaces on the ATM router
module interface support full ATM functionality.
Note These subinterfaces are not created by default.
The ATM router module supports LANE clients (LECs), but not the LANE servers (LES, LECS, and
BUS). It separates the control and data path so that all LANE control messages are handled by the route
processor, and all data messages are switched on the ATM router module port, as shown in Figure 13-2.
The LEC is configured on the ATM router module interface, but control message traffic is sent to the
route processor by the ATM router module. The ATM router module then sends all ATM data traffic to
the appropriate VCs.