Cisco Systems OL-1911-05 Manual ATM Router Module Interface Configuration, Command Purpose, 24-10

Chapter 24 Configuring ATM Router Module Interfaces

Configuring ATM Router Module Interfaces

Default ATM Router Module Interface Configuration Without Autoconfiguration

If ILMI is disabled or if the connecting end node does not support ILMI, the following defaults are assigned to all ATM router module interfaces:

•ATM interface type = UNI

•UNI version = 3.0

•Maximum VCI bits = 11

•MTU size = 1500 bytes

•ATM interface side = network

•ATM UNI type = private

Note Only Catalyst 8540 MSR enhanced ATM router module interfaces support IP unicast and IP multicast fragmentation. For IP unicast fragmentation, the packet must ingress on an enhanced ATM router module 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 enhanced ATM router module interface before being switched to other members in the multicast group. All the members in the multicast group must have an MTU equal to or greater than 1500 bytes.

Manual ATM Router Module Interface Configuration

To manually change the default configuration values, perform the following steps, beginning in global configuration mode:

	Command	Purpose
Step 1
	Switch(config)# interface atm card/subcard/port	Specifies an ATM interface and enters interface
	Switch(config-if)#	configuration mode.
Step 2
	Switch(config-if)# atm maxvci-bitsmax-vci-bits	Modifies the maximum number of active
		VCI bits.
Step 3
	Switch(config-if)# mtu bytes	Modifies the MTU size. The default MTU size is
		1500 bytes.
		Note Only Catalyst 8540 MSR enhanced ATM
		router modules support variable MTU
		sizes.

Example

The following example shows how to change the default number of active VCI bits:

Switch(config)# interface atm 0/0/0

Switch(config-if)# atm maxvci-bits 10

	ATM and Layer 3 Switch Router Software Configuration Guide
24-10	OL-1911-05