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mtu

 

Syntax

Hierarchy Level

Release Information

Statement introduced in Junos OS Release 11.1.

Description

Specify the maximum transmission unit (MTU) size for the media. Changing the media MTU size causes an interface to be deleted and added again. On QFX3500, QFX3600, QFX5100, and OCX Series switches, either standalone or as part of the QFabric system, the maximum MTU value on an untagged packet transiting through an ingress Gigabit Ethernet interface must be no more than the currently configured MTU value plus four, whereas the maximum MTU value on a tagged packet transiting through an ingress Gigabit Ethernet interface must be no more than the currently configured MTU value plus eight. The maximum MTU value on an untagged or tagged packet transiting through an ingress 10-Gigabit Ethernet interface must be no more than the currently configured MTU value plus eight.

On QFX5110 switches, setting MTU on the L3 interface does not take effect and packets with MTU greater than the default value are dropped.

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). On a QFX5100 switch jumbo frames on the RVI are configured on the basis of the interface MTU.

    Note

    RVIs are not supported on OCX Series switches.

    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.

Options

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.