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[EX] How to format install EX2300s and EX3400s via USB



Article ID: KB31265 KB Last Updated: 01 May 2020Version: 5.0

A switch can be recovered by performing a format installation with a bootable USB if it does not boot successfully. This article explains how the format installation can be performed on EX2300 and EX3400 switching devices.

Warning: This procedure will format the switch and all configurations will be lost.

For TFTP format install steps, please refer to: KB31462 - How to recover EX2300s and EX3400s with format install procedure via TFTP


To perform format installation on EX3400 and EX2300 switches, perform the following steps:

  1. Download the corresponding "USB" image under "Install Media" section from Juniper's Support site. 

  2. Transfer the image to a bootable USB. You can make a USB drive bootable by using the dd command in shell, or use GUI-based USB flash drive utilities such as Rufus or ISO Burner for Windows.

    Note: "img.gz" files may need to be extracted to "img."

  3. Insert the USB into the EX3400/EX2300 switch.

  4. Reboot the switch and interrupt the boot sequence. Use up/down arrow keys or press any key to interrupt the boot-up process; although if numbers or hotkey menu letters (e.i. [R]eboot) are used, you may select an undesired option. Example:

    U-Boot 2016.01-rc1 (May 23 2016 - 08:45:58 -0700) VERSION=1.2.0
    DRAM: AVS: 0x0
    DEV ID = 0xdc14
    SKU ID = 0xb548
    DDR type: DDR3
    MEMC 0 DDR speed = 750MHz
    PHY revision version: 0x00044006
    SF: Detected MX25L6405D with page size 256 Bytes, erase size 64 KiB, total 8 MiB
    In: serial
    Out: serial
    Err: serial
    FLASH bank: 1
    Board: EX3400-24P
    Base MAC: F4CC55CC9661
    Net: bcmiproc_eth-0
    Last Reset Reason: 8
    Hit ^C to stop autoboot: 0
    SF: Detected MX25L6405D with page size 256 Bytes, erase size 64 KiB, total 8 MiB
    device 0 offset 0x3c0000, size 0x10000
    SF: 65536 bytes @ 0x3c0000 Read: OK
    ## Checking Image at 61000000 ...
    Legacy image found
    Image Name: Juniper U-Boot Script File
    Image Type: ARM Unknown OS Script (uncompressed)
    Data Size: 1803 Bytes = 1.8 KiB
    Load Address: 00000000
    Entry Point: 00000000
    Image 0: 1795 Bytes = 1.8 KiB
    Verifying Checksum ... OK
    ## Executing script at 61000000
    Setting bus to 0
    SF: Detected MX25L6405D with page size 256 Bytes, erase size 64 KiB, total 8 MiB
    device 0 offset 0x140000, size 0x140000
    SF: 1310720 bytes @ 0x140000 Read: OK
    6113fffc: f1c1fb43 C...
    crc32 for 61000000 ... 6113ffff ==> 43fbc1f1
    Total of 1 word(s) were the same
    starting USB...
    USB0: phy ctrl 01d36440
    Initial usb2h clock is: 000003fc
    Initial usb2h clock is: 000003fd
    iClk = 00000078, USBClk = 01536440
    Bring usb2h_out of reset.......
    usb2_reset_state is set and now it is: 00000000
    usb2_reset_state is: 00000000
    USB EHCI 1.00
    scanning bus 0 for devices... 3 USB Device(s) found
    scanning usb for storage devices... 1 Storage Device(s) found
    SF: Detected MX25L6405D with page size 256 Bytes, erase size 64 KiB, total 8 MiB, mapped at 00000088
    ## Starting application at 0x00000074 ...
    Consoles: U-Boot console
    FreeBSD/armv6 U-Boot loader, Revision 1.2
    (, Wed May 18 12:32:06 PDT 2016)
    DRAM: 2048MB
    Number of U-Boot devices: 2
    U-Boot env: loaderdev not set, will probe all devices.
    Found U-Boot device: disk
    Probing all disk devices...
    Checking unit=0 slice=<auto> partition=<auto>... good.
    Main Menu
    1. Boot [J]unos volume
    2. Boot Junos volume in [S]afe mode
    3. [R]eboot
    4. [B]oot menu
    5. [M]ore options
  5. Press 4 for Boot Menu.

    Boot Menu
    1. Boot [P]revious installed Junos packages
    2. Boot Junos in [S]ingle user mode
    3. Boot from [R]ecovery snapshot
    4. Boot from [U]SB
    5. Boot to [O]AM shell
    6. Snapshot [B]oot menu
    7. [M]ain menu
  6. Press 4 again for boot from USB.

  7. You will see a message attempting to boot from USB.

  8. After the USB image installation is complete, log in and verify that the new version of the software is properly installed.

Modification History:

2020-04/30: Added reference link to KB31462.
2019-09-30: Minor modifications made to steps 1 and 2 in Solution section; image added to Step 1

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