Cisco Systems 8540 CSR Configuring Sonet Framing, Stm-1, Routerconfig-if# atm sonet, Stm-4

Chapter 4 Configuring Interfaces

Configuring the ATM Uplink Interface (Catalyst 8540)

Note The ATM uplink supports IP unicast and IP multicast fragmentation. For IP unicast fragmentation, the packet must ingress on a ATM interface and egress on any interface. For IP multicast fragmentation, IP multicast data packets greater than 1500 bytes are fragmented to 1500 bytes on the ingress ATM interface before being switched to other members in the multicast group. All the members in the multicast group must have a MTU equal to or greater than 1500 bytes.

Configuring SONET Framing

In STM-1 mode or STM-4 mode, the ATM uplink interface sends idle cells for cell-rate decoupling. In STS-3c mode or STS-12c mode, the interface sends unassigned cells for cell-rate decoupling. STS-3c is the default SONET framing mode for the ATM OC-3c uplink interface; STS-12c is the default SONET framing mode for the ATM OC-12c uplink interface.

To configure the SONET framing mode, perform the following steps, beginning in global configuration mode:

	Command	Purpose
Step 1
	Router(config)# interface atm	Enters interface configuration mode and specifies the ATM
	slot/subslot/interface	interface to configure.
	Router(config-if)#
Step 2
	Router(config-if)# atm sonet	Configures the SONET framing mode to STM-1 (for the OC-3c
	stm-1	ATM interface) or to STM-4 (for the OC-12c interface).
	or
	Router(config-if)# atm sonet
	stm-4
Step 3
	Router(config-if)# no shutdown	Enables the interface with the previous configuration.

To return the SONET framing mode to the default, use the no form of the atm sonet command.

Configuring SONET Overhead

You can use the sonet overhead command to set the SONET overhead bytes in the frame header to meet a specific standards requirement or to ensure interoperability of the ATM uplink interface with another vendor's equipment. You can use the no form of this command to restore default values.

	Layer 3 Switching Software Feature and Configuration Guide
78-6235-04, Cisco IOS Release 12.0(10)W5(18)		4-31