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[EX] How to update the system MAC address of EX4300VC when 'mac-persistence-timer' is disabled



Article ID: KB28757 KB Last Updated: 30 Mar 2021Version: 3.0

This article describes how to update the system MAC address of EX4300VC, when mac-persistence-timer is disabled.


Initially, based on the MAC address of the primary, the system MAC address is selected. However, if mac-persistence-timer is disabled, the system MAC address will never change, even if the primary has to be replaced.

A similar article, KB26767, describes how to update the mac-persistence-timer of EX Series devices except the EX4300. But since the method is different between EX4300 and other EXs, please follow the instructions in this article for EX4300.

For more information on system MAC address, please refer to the following link:

Understanding MAC Address Assignment on a Virtual Chassis


If there is no risk of a duplicate MAC address, you can continue to use the system MAC address, based on the previous primary that was replaced. However, if you would like to use the previous primary in the network, but not as a member of the virtual chassis, the system MAC address has to be updated.

To update the system MAC address after replacing the previous primary, use any of the following methods during maintenance time. These methods may affect the traffic that passes through the virtual chassis:

Method 1:

Reboot the whole chassis in the virtual chassis.

If  it is not possible to implement this, then please use Method 2.

Method 2:

  1. Configuration change:
    deactivate virtual-chassis mac-persistence-timer disable
    set virtual-chassis mac-persistence-timer 1
  2. Switch over by using the command request chassis routing-engine master switch.

  3. Wait for 1 minute or longer:
    *If you have lacp setting, lacp will be flapped to change its MAC address.

  5. Recover the configuration:
    delete virtual-chassis mac-persistence-timer 1
    activate virtual-chassis mac-persistence-timer disable
Modification History:
2021-03-24: Updated the article terminology to align with Juniper's Inclusion & Diversity initiatives.
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