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24-10
ATM and Layer 3 Switch Router Software Configuration Guide
OL-1911-05
Chapter 24 Configuring ATM Router Module Interfaces
Configuring ATM Router Module Interfaces
DefaultATMRouterModuleInterfaceConfigurationWithoutAutoconfiguration
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:
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
Command Purpose
Step 1
Switch(config)# interface atm card/subcard/port
Switch(config-if)#
Specifies an ATM interface and enters interface
configuration mode.
Step 2
Switch(config-if)# atm maxvci-bits max-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.