Command Reference Guide

3Com Router 5000 Family and Router 6000 Family mtu ● 237
Command Reference
mtu
Purpose Use the mtu command to set the size of Maximum Transmission Unit (MTU) of the ATM
interface.
Use the undo mtu command to restore the default of the value.
Syntax mtu mtu-number
undo mtu
Parameters mtu-number
MTU size of ATM interface (in bytes). Valid values are
128 to 2000.
If no value is specified, the default is 1500 bytes.
Example Display how to set MTU of ATM interface Atm1/0/0 to 1492 bytes.
[3Com-Atm1/0/0] mtu 1492
View This command can be used in the following views:
■ Interface view
Description MTU of ATM interface only influences the packet assembling and packet
disassembling of IP layer at the ATM interface. Because of the limit of the QoS queue
length (for example, the default length of the FIFO queue is 75), the too small MTU
will lead to too many fragments and will be dropped by the QoS queue. In this case,
the length of the QoS queue can be enlarged appropriately. FIFO is the queue
dispatching mechanism used by PVC by default, and its queue length can be changed
by using the
fifo queue-length command in the PVC view.
This command can be used in ATM main interface and sub-interface at the same
time.