Configuring atm router module interfaces – Cisco ATM and Layer 3 Switch Router OL-1911-05 User Manual

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ATM and Layer 3 Switch Router Software Configuration Guide


Chapter 24

Configuring ATM Router Module Interfaces

Configuring ATM Router Module Interfaces

IP fragmentation.

IP 6-path load balancing.


The ATM router module is only supported on ATM switches which have a multiservice ATM switch
processor installed.


The LightStream 1010 system software image does not include support for the ATM router module
or Layer 3 features. You can download this image to a LightStream 1010 ATM switch router with a
multiservice ATM switch processor installed.

Configuring ATM Router Module Interfaces

The you can configure the following features directly on the ATM router module interfaces:

Maximum virtual channel identifier (VCI) bits

Maximum Transmission Units (MTUs) (enhanced Catalyst 8540 MSR)

LANE clients (Catalyst 8540 MSR)

RFC 1483

Classical IP over ATM (RFC 1577)


IP multicast


This document describes how to configure ATM software features combined with Layer 3 features
only. For more detailed information on how to configure the Layer 3 modules that interoperate with
the ATM router module in the Catalyst 8540 MSR chassis, refer to the Layer 3 Switching Software
Feature and Configuration Guide
, which is available on the Documentation CD-ROM that came with
your ATM switch router, online at

, or when ordered separately as a hard copy document.


ATM router modules have internal interfaces, but no external ports. Use the interface atm
card/subcard/port command to specify these interfaces.


Virtual path identifier (VPI) 2 is reserved for ATM router module interfaces, which allows up to 2048
external VCs on each ATM router module interface. Using VPI 0 would have allowed less than 1024
external VCs on an ATM router module interface because the ATM router module external VCs
would have been forced to share the VC space within VPI 0 with the internal PVCs.

Even though each ATM router module interface supports a maximum of 2048 VCs, only
1400 to 1500 external VCs can be configured. Internal VCs use up the rest.