Cisco Cisco IOS Software Release 12.0(22)S

See the following sections for configuration tasks for the 8-Port OC-3 STM-1 ATM line card.

The interface of the 8-Port OC-3 STM-1 ATM line card interface is referred to as “atm” in the 
configuration commands. An interface is created for each 8-Port OC-3 STM-1 ATM line card found in 
the system at reset time. 

To select a specific 8-Port OC-3 STM-1 ATM line card interface, use the interface atm 
slot/port.subifnum command:

Router(config)# interface atm slot/port.subifnum

A virtual circuit (VC) is a point-to-point connection between two ATM devices. A virtual circuit is 
established for each ATM end node with which the router communicates. The characteristics of the 
virtual circuit are established when the virtual circuit is created and include the following for the 8-Port 
OC-3 STM-1 ATM line card:

Quality of service (QoS)

ATM adaptation layer (AAL) mode (AAL5 only)

Encapsulation type (LLC/SNAP, IP MUX, and NLPID)

Peak and average transmission rates

Each permanent virtual circuit (PVC) configured on the router remains active until the circuit is removed 
from the configuration. All virtual circuit characteristics apply to PVCs. When a PVC is configured, all 
configuration options are passed to the 8-Port OC-3 STM-1 ATM line card. These PVCs are written to 
the nonvolatile RAM (NVRAM) as part of the configuration and are used when the Cisco IOS image is 
reloaded.

When you create a PVC, you create a virtual circuit descriptor (VCD) and attach it to the VPI and VCI. 
The VCD tells the card which VPI/VCI to use for a particular packet. The 8-Port OC-3 STM-1 ATM line 
card requires this feature to manage the packets for transmission. The number chosen for the VCD is 
independent of the VPI/VCI used.