Import settings to new firmware? How and why not if router does it?

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Regular Contributor
Ok, just let me be clear.

It is totaly logical for me NOT to import old settings backup to a new(er) firmware... I always configure it from scratch after updating.

However, I have a question...

So lets say, that I have a Asus router with an older firmware and I want to flash a newer one.

No problem. Upload a newer firmware and voila, the router is updated WITH AN OLD SETTINGS! How is THAT possbile, that the settings are still there, functioning normally, but it would be not recommended to upload older settings MANUALLY after flashing the new firmware. How come the new firmware is still working with an old settings from previous firmware?!

Just a theoretical question of course, thats all, hopefully I am being clear...

Thanks for the answer(s)!


Very Senior Member
Generally the old nvram variables and settings are close enough that it often *appears* (and may actually be) working properly. But that's not always the case. Things may change, and when that happens, you risk having your old nvram settings out-of-sync w/ the new firmware. Making it a habit to *always* manually reconfigure when installing new firmware eliminates that risk.

There are ppl who, despite those risks, will perform "dirty upgrades" anyway. To each his own.
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Part of the Furniture
The new firmware is appearing to work with the old settings. Great illusionist!

It may stay that way for many days/months or years, depending on the specifics of the network and the features, options, and network expectations of the owner.

When we flash new firmware, and the router gets messed up, we need to perform a full reset to factory defaults on it. Not the 'factory defaults' it was shipped with, but to the defaults, the firmware is expecting to see and use.

At this point, if we now restore an old backup config file with old settings, we have effectively undone the full reset we performed.

The reason we need to do a reset in the first place is that the variables, functions, and defaults change over the course of firmware development, and allowing this old, lingering code on new firmware is just asking for trouble that can never be easily tracked down and corrected. It is far easier to just reset than understanding the interactions that may be happening under the hood.

For some, a reset is needed, sooner, for others, later, but for sure, it is needed by all, eventually.

[FAQ] NVRAM and Factory Default Reset | SmallNetBuilder Forums (


Regular Contributor
So, by this logic, "dirty" upgrades should not even exist, in the means of using the router as stable after such flashes.

Furthermore, the router should then ALWAYS be fully resetted (nuked... :D), even for minor upgrades such as for example 384.14 to 384.14_2 or like that...



Very Senior Member
I think the key information is that some settings are not visible to us in the GUI but are used internally by the router. Therefore we never know if these defaults change from version to version.

My view is slightly different that ASUS know this and “should” tell us when they release a version that MUST have a reset, however they have many developers and may not always capture each occasion. RMerlin certainly doesn’t always know for his firmware but will give us a hint.

So from experience many members here advocate a factory reset after every update to be on the safe side. It’s a belt and braces approach that will make sure you have the latest hidden defaults, but at the cost of time to reconfigure.

I take a pragmatic view, read the release notes and usually don’t bother for minor updates, but usually do for major updates.

Its personal choice based on time/effort vs risk of instability


Part of the Furniture
@sl4fko for my customers, there is no choice, you are correct. I don't want to reschedule an appointment, waste time driving, and other unnecessarily repeated things when I could just do it properly while I'm there.

For many here in the forums who are only looking after their own network, they have the luxury to wait and see if the dirty upgrade changed things for the worst, before doing a full reset.

For myself, I used to just do a full reset on my network 'for fun', and to have it be the most stable as can be.

For the last year or so, I've been having just as much fun seeing how long I can go 'dirty' (like a teenage athlete) before I need to clean up the network again.

The 2x RT-AX86U's in wired AiMesh mode I've had for a short time now have not had the luxury of being reset (yet) since flashing 386.1 Beta 1 when it became available.

Although the network is more than just 'usable', I know it can be better once I've fully and properly reset it using the steps and suggestions outlined below.

Best Practice Update/Setup Router/AiMesh Node(s) 2021

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