The maximum transmission unit (MTU) determines the maximum number of bytes that can be sent by a device at a time. If the MTU exceeds the maximum number of bytes supported by the receiving device or a device along the transmission path, packets are fragmented or even discarded, increasing traffic loads on the network. You can configure the MTU based on the actual network environment.

Only Layer 3 interfaces support the MTU configuration. By default, the MTU of MTunnel interface is 1472 bytes, and other interfaces is 1500 bytes. You can run the mtu command in the interface view to change the MTU of a Layer 3 interface.

# configure the MTU of a common physical interface.

<HUAWEI> system-view
[~HUAWEI] interface 10ge 1/17/1
[~HUAWEI-10GE1/17/1] undo portswitch  //Switch the interface to Layer 3 mode.
[*HUAWEI-10GE1/17/1] mtu 1200
[*HUAWEI-10GE1/17/1] commit

# configure the MTU of a VLANIF interface.

<HUAWEI> system-view
[~HUAWEI] interface Vlanif 100
[*HUAWEI-Vlanif100] mtu 1200 
[*HUAWEI-Vlanif100] commit