Description

Jumbo frames can be configured on the physical interfaces on the Juniper Networks EX/QFX Series Switches.

Jumbo frames are Ethernet frames with more than 1,500 bytes of payload (Maximum Transmission Unit, MTU). Jumbo frames can carry up to 9,000 bytes of payload.

Symptoms

You want to find out the maximum MTU size for an interface.

Solution

Jumbo frames can be configured on the EX/QFX series Switches using 2 methods, the CLI (Command Line Interface) and J-Web interface.

Configuration using the CLI:

user@switch# set interfaces ge-0/0/0 mtu 9216      

(Maximum transmit packet size (256..9216))

Configuration using J-Web interface:

  1. Point your web browser to the management interface of the switch
  2. Log in to the EX/QFX series switch using the credentials you have provisioned.
  3. Once the Login is successful, you will be presented to the Dashboard page. Click the Configure Tab at the top.
  4. At this page, select the interface that needs to be enabled for jumbo frames.
  5. Click the 'Edit' button on the top right portion of the screen.
  6. Select Link options and set the MTU size to 9216. (Allowed values are 256 bytes - 9216 bytes)

Below are the steps on how to enable Jumbo frames on an aggregate interface on EX/QFX series switches

The following is the set of command to create a link aggregation bundle and enable jumbo frames:
{master:0}[edit interfaces ge-0/0/0]
user@switch# show
unit 0 {
    family ethernet-switching;
}

{master:0}[edit interfaces ge-0/0/0]
user@switch# delete unit 0

{master:0}[edit interfaces ge-0/0/0]
user@switch# show | compare
[edit interfaces ge-0/0/0]
unit 0 {
   family ethernet-switching;
}

user@switch# set chassis aggregated-devices ethernet device-count 4 >>>>4 LAG bundles can be created from 0-3
user@switch# set interfaces ge-0/0/40 ether-options 802.3ad ae0
user@switch# set interfaces ge-0/0/42 ether-options 802.3ad ae0
user@switch# set interfaces ae0 mtu 9200

In order to confirm the maximum jumbo frame to be configured on the port you can use a "?" on the interface settings:

{master:0}[edit]
user@switch# set interfaces ae0 mtu ?
Possible completions:
  <mtu>                Maximum transmit packet size (256..9216)


Note: MTU can only be set on the aggregated interface, not on the child member.
 
 

Modification History

2020-02-18: Article reviewed for accuracy; no changes required.
2023-05-12: KB edited to show how to find the max MTU.