MG90s performing firmware upgrade via the AMM may require installation of intermediate transition firmware.

Date of Issue: September 11, 2018

Applicable Products

MG90 routers that are upgrading to MGOS 4.2.0 or later firmware via the AMM, and are

  • operating with MGOS 4.1 or later firmware and upgrading for the first-time or
  • operating with MGOS 4.0.x firmware

Exempt products:

MG90s that have previously upgraded to MGOS 4.1 or later firmware via AMM or USB stick install are not affected. MG90s upgrading from MGOS 4.2.1 or later firmware are also not affected.


MG90 routers upgrading from MGOS 4.2.0 or earlier firmware via the AMM, may need to first install transition firmware before upgrading to the latest. The required transition firmware will depend on the current operating firmware version.

a)    MG90s operating with MGOS 4.1 or later firmware

Transition firmware is required only if the MG90 is running original shipped firmware, i.e. the device has not previously performed a firmware upgrade.
Figure 1: AMM Update path from MGOS 4.1.0 or later firmware
Failure to install the transition firmware prior to upgrading to the latest firmware via the AMM will result in an upgrade failure. If this occurs, the AMM’s Software Distribution page will display ‘Insufficient disk space for downloading tarballs’.

b)    MG90s operating with MGOS 4.0.x firmware version

All MG90s upgrading from MGOS 4.0.x via the AMM must first upgrade to MGOS 4.1 before upgrading to the latest.
Figure 2: AMM Update path from MGOS 4.0.x firmware

Recommended Steps

Sierra Wireless advises customers with affected units wishing to perform an AMM-based firmware upgrade to follow the steps below or contact Sierra Wireless Support for assistance.

  1. Identify the appropriate transition firmware required, based on the current MGOS firmware version on the router.
Current MGOS Firmware Required Transition Firmware
MGOS 4.1, 4.1.2 MGOS
MGOS 4.0.3, 4.0.4, 4.0.5 MGOS 4.1
  1. Upgrade to the required transition firmware.
  2. Promptly upgrade to the latest firmware.


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