Understanding Avaya / Nortel AUR, AAUR, DAUR and LAUR features when replacing a failed unit in a stack

So lets describe what each of these acronyms stand for and then explain what they do when you replace a failed stack unit.

**NOTE** Depending on your switch model and software version not all of these features are available.  Please read the documentation for an understand of what features are supported on your platform.

AUR

 Auto Unit Replacement (or automatic unit replacement).

Function:  This feature is responsible for replacing the failed unit's configuration onto the replacement device.  The replacement device will automatically reset after AUR has copied the configuration.

AAUR

 Agent Auto Unit Replacement.

Function:  This feature is responsible for replacing the failed unit's image(software) onto the replacement device.  The replacement device will automatically reset after AAUR has copied the image (software).

DAUR

 Diagnostics Auto Unit Replacement.

Function:  This feature is responsible for replacing the failed unit's firmware(diagnostics) onto the replacement device.  The replacement device will automatically reset after DAUR has copied the  firmware(diagnostics).

LAUR

 Licensing Auto Unit Replacement.

Function:  This feature is not like the others, it actually builds a virtual license, based on the loaded license file and the MAC address of the stack.  The stack continues to use the virtual license file even if the base unit fails and is replaced.  "This means that you do not need to regenerate a new license file when you replace a failed base unit in a stack.




Actual Operation of these features

So lets walk through the replacement process.  Say we have a stack of 4x ERS4524GT switches and unit #4 fails.  Luckily we work in the perfect workplace and we have a spare ERS4524GT switch on the shelf, but we are unsure of what state the config is in or what software is actually running on the switch.  Not to worry we can replace the failed unit with no issues as its the same hardware type as the switch that failed.

Now the following steps would be.

1. Remove old switch from the stack.
2. Insert new switch into stack, connecting stacking cables, its best to leave the front ports unpactched at this stage and  do not power up the replacement unit.
3. Check the base switch on the replacement unit is off (we are replacing unit#4 remember)
4. Power on the replacement unit.
5. Device will boot up, DAUR on the stack will detect if the firmware(diagnostics) is the same in the replacement unit as is what is running on the stack.  If an upgrade is required DAUR will download the firmware(diagnostics) to the replacement unit and reboot that unit only.  If DAUR has determined no upgrade is required then nothing more will be performed by this feature.
6. Once DAUR has upgraded or determined no firmware(diagnostics) upgrade is required, AAUR will detect if the image(software) is the same in the replacement unit as is what is running on the stack.  If an upgrade is required AAUR will download the image(software) to the replacement unit and reboot that unit only.  If AAUR has determined no upgrade is required then nothing more will be performed by this feature.
7.  Once AAUR has upgraded or determined no image(software)upgrade is required, AUR will download the replacement configuration of the failed unit to the replacement unit and reboot that unit only.
8. Once the unit has has rebooted for the final time (which could have been 3x times!!) you can now connect all the front ports
9. Confirm stack operation with "show stack-info" and "show stack health" commands

 Hopefully if you are new to Avaya / Nortel stackable switches this guide has helped you somewhat.  


Please leave a comment if you have any questions or if you have found this guide to be useful.  I will attempt to get back to you in a timely manner.