Technical Documentation



mtu bytes;

Hierarchy Level

[edit interfaces interface-name]

Release Information

Statement introduced in JUNOS Release 9.0 for EX Series switches.


Specify the maximum transmission unit (MTU) size for the media. Changing the media MTU size causes an interface to be deleted and added again. Keep the following points in mind if you are configuring MTU size for jumbo frames on these special types of interfaces:

  • For LAG interfaces—Configuring the jumbo MTU size on a link aggregation group (LAG) interface (aex) automatically configures the jumbo MTU size on the member links.
  • For RVIs—Jumbo frames of up to 9216 bytes are supported on the routed VLAN interface (RVI), which is named vlan. The RVI functions as a logical router. To route jumbo data packets on the RVI, you must configure the jumbo MTU size on the member physical interfaces of the RVI and not on the RVI itself (the vlan interface). However, for jumbo control packets—for example, to ping the RVI with a packet size of 6000 bytes or more—you must explicitly configure the jumbo MTU size on the interface named vlan (the RVI).

    Caution: Setting or deleting the jumbo MTU size on the RVI (the vlan interface) while the switch is transmitting packets might result in dropped packets.


1514 bytes


bytes—MTU size.

Range: 64 through 9216 bytes
Default: 1514 bytes

Required Privilege Level

interface—To view this statement in the configuration.
interface-control—To add this statement to the configuration.

Published: 2009-09-16