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ERS Stackable: How To Upgrade and Replace a Unit In Stack

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TitleERS Stackable: How To Upgrade and Replace a Unit In Stack
ERS Stackable: How To Upgrade and Replace a Unit In Stack
  • BOSS stackable switch models

Procedure to upgrade the stack:

Ethernet Routing Switch Stackable running any supported software version.

1.  Before performing any kind of activity, please keep the config back-up of the entire stack as well as of the faulty unit (or) the unit which is intended to be replaced.

2.  Use below commands to download a new Agent (Software) and Diagnostic (Firmware) Images onto the stack. Make sure that the TFTP server has both the files and should be reachable to the Stack Base unit as these files would be pushed to the Base Unit only.

    download address diag                 /  to download the Diagnostic Image to the stack.
    download address image             /  to download the Agent Image to the stack.

Below commands can be used to take Configuration backup from the stack by connecting to the Base unit of the stack:
    copy config tftp address filename                       / to copy configuration (Binary) to the tftp server from Base unit.
    copy running-config tftp address filename        / to copy configuration (ASCII) to the tftp server from Base unit.

Below commands can be used to push the backup configuration to the stack from TFTP Server:
    copy tftp config address filename                       /to load configuration (Binary) to the Base unit from tftp server.
    configure network address filename               /to load configuration (ASCII) to the Base unit from tftp server


Command to backup configuration in ASCII format using USB:

copy running-config usb filename <file-name>


Command to backup configuration in binary format using USB:

copy config usb filename <file-name>


Command to restore configuration using USB:

copy usb config filename <name>


copy usb config filename <name>Note: Every time a Image is downloaded to the stack, the stack would reboot by itself and the downloaded image would override the existing one on the stack. For stack to upgrade to the newly downloaded images, it has to reboot. If you don't want to reboot the stack right after the image files are downloaded, use "no-reset" at the end of the commands. Please find the below commands mentioning the same:

    download address diag no-reset         /to download the Diagnostic Image to the stack.
    download address image no-reset      /to download the Agent Image to the stack.   

ERS Stackable - Replacing a unit (faulty unit) on the running stack.

1.       Power up the new unit (standalone switch) and verify the status of the rear stack/standalone ports status with command show rear-ports mode and change it to stacking mode with the help of command rear-ports mode stacking.

2.       Before removing the faulty unit from the stack check show stack auto-unit-replacement and show autosave on the stack. If both these features are enabled, then the configuration from the base unit of the stack will be pushed automatically to the new joining unit.
3.       In case,  if show stack auto-unit-replacement and show autosave are disabled on the stack, end-users need to manually push the configuration to the new unit with the help of its last saved configuration backup taken. Else, if end-users have configuration back up of the entire stack before faulty unit was replaced, then they can push the stack config again to the base unit after adding the new unit..
4.       Before adding the new unit to the stack, please verify whether AAUR function on the stack (base unit) is enabled. If not, enable with the help of command stack auto-unit-replacement-image enable and verify again with show stack auto-unit-replacement-image.

Note:  If Base unit is being replaced, be sure to change the Base unit switch (on back of unit) to Base.  By default, this switch is set to Non-Base.

Note: AAUR is recommended and enabled by default. This feature enables the base unit of the stack to upgrade the software (run time image) of the newly added switch automatically. If stack is running on software code 5.1 or above, then along with AAUR, DAUR is also enabled and it would upgrade the diag image of the newly added unit after connecting to the stack. If software version of the stack is below 5.1 code, upgrade the diag on the new unit manually as that of stack (base unit ) diag image(firmware image).

5.       Once the new unit is added to the stack, wait for few minutes for the newly added unit to come up in stack with the same Agent and the Diagnostic Image as that of the Base unit.
6.       Once the stack upgrade and replacement is done, issue commands show stack-info and  show stack health to verify.

Note: It is recommended that the new unit runs the same version of Diagnostics image as that of the stack base unit. Ensure that the replacement unit's knob is set to Non Base at the back. While replacing the unit, Stack must be powered on because configuration images are retained in the stack DRAM.

Normally, the base unit should upgrade a newly added switch automatically. But there are instances where it doesn't work causing configuration loss. The reason for this could be a faulty base unit which functions normally causing no impact to services, but the sync feature of base works improper when it comes to uploading the images of 15 to 19Mb size to the replaced unit.  This leads to config loss and the newly replaced unit doesn't add up to the stack. A part of Configuration specific to replaced unit might get lost.

How AAUR works?

  • When added a replaced unit to an AAUR-enabled stack, AAUR compares the switch software image on the replacement unit to the stack software image.
  • If the replaced unit Agent image differs from the stack (base unit) Agent image then AAUR downloads the Agent image from the base unit to the replaced unit.
  • The system resets the new unit.
  • The new unit then becomes a member of the stack after reboot.

How AUR works?

  • Auto Unit Replacement (AUR) is enabled by default and restores the configuration of the unit which was replaced by a new one in the stack. The new unit must be of the same hardware model.
  • After starting a stack, use ACLI command show stack auto-unit-replacement from a unit console to find out if that unit is ready for replacement.

    NOTE: 'AUR' does not work in a stack of two units only.

What is DAUR?

  • Diagnostic Auto Unit Replacement is responsible for replacing the Diagnostic Image (Firmware Image) on the newly added unit to the stack. Diagnostic Auto Unit Replacement (DAUR) is configured with AAUR. There are no commands to separately enable DAUR.

    Note: The replaced device will automatically reset after DAUR has copied the Diagnostic Image (Firmware Image)


  • The Stack operates in 2 modes Pure & Hybrid. Pure stack is a stack consisting of only ERS45xx, ERS48xx, ERS55xx or ERS56xx Switches .Hybrid is a mix of ERS55xx and ERS56xx units (or ERS45xx and ERS48xx units) in the same stack.
  • AUR and AAUR enhancement as of release 5.10:  Auto Unit Replacement (AUR) and Agent Auto Unit Replacement (AAUR) features are enhanced to support base unit replacement for a stack of two switches.
Additional notes



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