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[ScreenOS] Downgrade bootloader to an older version?

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Summary:

This article answers the question, "Can the bootloader on a firewall be downgraded to an older version?

Symptoms:

Example Scenario

A ScreenOS on a firewall in an NSRP cluster is upgraded.

A short while later, a decision is made to roll back the upgrade to the old version.

Temporarily, the firewalls are running different versions of the ScreenOS and different versions of the bootloader, as explained below:

  • Firewall A is on Screen OS 6.1.0r5 with v116.d bootloader.

  • Firewall B is on Screen OS 6.0.0r8 with v115.d bootloader.

  • Note that the bootloader is upgraded in order to upgrade the ScreenOS.

If Firewall A is downgraded back to Screen OS 6.0.0r8, it will still have the newer bootloader, and thus the firewalls will be different.

At this point, the question is: "Can the bootloader be downgraded?"

Cause:

The firewalls are running different versions of the ScreenOS and different versions of the bootloader.

Solution:

Install the correct versions of the ScreenOS and the correct versions of the bootloader.

Perform the procedure below to install the correct versions.

Note that the key to this situation is the bootloader: It is backward-compatible.

1. Download the ScreenOS and bootloader software (available from the same page as the ScreenOS downloads).

2. Install the software on the firewall with one of the following options:

Notes

  • In ScreenOS, the instructions for downgrading software are the same as the instructions for upgrading software, except that the filename of the ScreenOS image or bootloader is different.

  • A downgrade can be performed only via the CLI.
  • For step-by-step instructions on upgrading the bootloader and ScreenOS, see the ScreenOS Upgrade Guide.

    • Go to the ScreenOS Documentation link.

    • Click your Release version.

    • Click the Upgrade Guide (for ScreenOS 6.0 and above), or click the Release Notes (for ScreenOS 5.4 and below).

    • Refer to these chapters: Uploading Boot Loaders, Downloading New Firmware, and Upgrading to New Firmware.

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