We are using Cisco 3662 with OC-3 ATM interfaces. I have configured the interface and sub-interfaces with a MTU of 9000. However, when I run extended ping with a sweep range of 56 bytes to 8500 bytes, the pings timeout at approximately 4000 bytes. The timeout is set for 2 seconds. I have noticed when I use a "show interface atm 2/0" that the "length violation" increased but not the crc.
The OC-3 interfaces are connected to Macroni ASX-1200 switch. The ASX used UBR. The router interface is configured as a PVC 10/30 using AAL5Snap.
How can I achieve a large MTU throughtput? What is the maximum MTU that can be achieved through a OC-3 interface?