Got One of These Asus Routers? Sprinkle Some Merlin Magic on It!

RT AX88U vs RT AC88U 4
The Asus RT-AX88U (left) and RT-AC88U are excellent candidates for Merlin firmware.

No, I’m not talking about wizards, but just regular Wi-Fi tech, which is cooler than magic anyway. So yes, if you’re interested in making your Asus router (even) better, you’re reading the right post. It’s all about replacing your router’s stock firmware with the Merlin alternative.

Dong’s note: Putting third-party firmware on a router, among other things, can be tricky and even cause the router to die if you don’t do it right. Consider yourself warned.

What is firmware?

Firmware is like a mini operating system. Every piece of tech gadget or electronics has to have run on a piece of software. So firmware to a router is kind of like Windows 10 to a computer. It decides how (well) the router functions and dictates what you can do with it.

Firmware vs. operating system

Both firmware and operating systems manipulate the hardware to deliver specific results. But they differ in nuances.

Specifaly, firmware has low-level — more direct and crude — access to the hardware. It’s geeky and closely related to a device’s physical components.

On the other hand, an operating system has higher, safer, and more refined access to the hardware. It’s user-friendly and about giving users what they want instead of dealing with hardware components’ basic functions.

A crude analogy: Firmware is like the wiring and switches under the hood of a car, while the operating system consists of the driving wheel, control buttons, and other shiny things inside the cabin. Most drivers only care about the latter and have no interest in the former, which, among other things, will make their hands dirty.

On a computer, the motherboard itself uses firmware, called BIOS, that decides what kind of computer it is and which operating system — Windows, Linux, or macOS, for example — you can install on it and how.

In some situations, though, the line between firmware and an operating system is a blur, and you can call the two interchangeably. For example, the firmware of Synology routers or Netgear’s gaming ones are so advanced that folks call those operating systems.

But generally, devices with limited functions, like the Internet of Things (IoT) gadgets, use firmware. And advanced devices, such as smartphones, tablets, or computers, use an operating system (on top of a firmware layer).

So, for the most part, Wi-Fi routers use firmware. But if you want to call that an operating system, that’s fine with me, too.

Asus WebUI Main
The web interface of an Asus RT-AC88U running stock firmware. Note the differences when it runs Merlin below.

Stock router firmware

By default, the networking vendor ships their routers its firmware already installed. That’s called “stock firmware” and in most cases, you can’t change it.

You may be able to upgrade the firmware to a newer/better version once in a while, but for the most part, the router’s features remain the same for the rest of its life.

Asus’s stock firmware, called Asuswrt, is used in all Asus’s home routers released in the past decade. (By the way, WRT stands for Wireless Receiver / Transmitter. It’s a common acronym in Wi-Fi broadcasters.)

Merlin: Special third-party firmware

With some routers, you can put a third-party firmware on it. Popular open-source router firmware, such as DDWRT, can work on (select) routers from multiple networking vendors. They tend to be completely different from the stock firmware and, therefore, quite hard to handle.

On the other hand, Merlin is the third-party firmware available only to certain Asus routers. It’s also very similar to Asus’s stock firmware. In fact, you can see it as an enhanced version of Asuswrt. What’s most important, for the most part, Merlin is as easy-to-use as Asuswrt.

Merlin Web UI Main
The interface of the RT-AC88U running Merlin. Note the Merlin logo.

Asus routers that can run Merlin

Here is the list of current Asus routers that you can put Merlin firmware on.

  • Wi-Fi 5 routers: RT-AC66U_B1, RT-AC86U, RT-N66U, RT-AC1900, RT-AC87U, RT-AC5300, RT-AC3200, RT-AC3100, RT-AC88U, RT-AC68U, RT-AC66U, RT-AC56U
  • Wi-Fi 6 routers: RT-AX56U, RT-AX58U (a.k.a RT-AX3000), RT-AX88U.

So, as you can see, not all Asus routers can run Merlin. There sure will be more in the future but, as to which, we have to wait and see.

In my experience, the RT-AC88U and RT-AX88U are currently the best Merlin options since they have the most to offer. But all the above will work similarly, in terms of settings and features.

Merlin vs. Asus stock firmware

Asus builds its Asuswrt using Linux via the GNU Project and shares its source code via GNU’s General Public License (GPL). Then, the Merlin group, led by Eric Sauvageau, changes the source code to create a better alternative. For free. (They do accept support via donation.)

In other words, Merlin is based on the stock firmware and, therefore, always becomes available, if at all, (long) after the release of a router.

Still, it’s not a surprise that its official name is Asuswrt-Merlin, though some might call it MerlinWRT. I’d call it Merlin for short. Merlin itself is also open-source software.

That said, generally, Merlin has all the settings and features of the stock firmware and then some. In other words, for a particular router, Merlin firmware encompasses its stock firmware.

Merlin’s features

Merlin TOR
The Merlin firmware has a lot of more feature and in-depth settings compared to the stock firmware, including the support for TOR.

Here’s the complete list of Merlin’s features, but the shortlist of benefits includes:

  • Better VPN support, which, among other things, has the ability to route certain clients via VPN or globally.
  • More flexible DNS — you can set the DNS server for individual clients or globally.
  • Built-in TOR support for privacy, with the individual client control, can route certain clients via TOR or globally.
  • Battery handles of bugs and generally more frequent firmware updates.
  • Better stability.
  • Lots of control, feature, and automate options via user scripts and add-on packages.
  • Excellent AiMesh support (starting with version 384).

Notes on moving between Asus stock firmware and Merlin

Generally, Asuswrt and Asuswrt-Merlin are very friendly toward each other. That means:

  • You can move a router between these two firmware options at any time. Specifically, you can flash a router from Asuswrt to Merlin, and all of its settings will remain the same. The other way around, though, only common settings between the two will remain.
  • You can restore a router using a setting backup file of either firmware. And, just like stock firmware, you can restore the settings of one router to another. In this case, though, depending on the routers involved, note that some settings might not be carried over.
  • The Asus Router mobile app (made by Asus) also works with a router running Merlin firmware.
  • Overall, Merlin’s web interface looks and feels the same as does Asus’s stock firmware. You might not even notice that you’re using Merlin.
  • The AiMesh feature is available in Merlin (starting with version 384), and you can use routers of either firmware together.

Merlin and AiMesh

Note, though, that you generally want to use AiMesh with the same firmware (Asuswrt or Merlin).

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In my testing, things are fine when you use Merlin in the main router. When I used Asuswrt in the main router and Merlin in a node, it was impossible to update the node’s firmware successfully. I’d have to reset the node, put the new firmware on it in the router mode, and then re-added it back to the mesh.

But that’s about the only shortcoming of using Merlin, which doesn’t exist if you use Merlin throughout. Also, the performance of a mixed system proved to be fast and reliable in my trial.

Asus’s take on Merlin

Asus didn’t give me any opinion on Merlin. Instead, it only said that it provided Asuswrt’s code as an open-source under GPL, as mentioned above.

But the company did tell me one thing that’s very important: Putting Merlin on Asus hardware will not affect its warranty. Specifically, a representative told me:

“[…] as long as the router does not break/fail during the firmware change process, we will still provide the warranty for the hardware. The 3rd party software is not tested by ASUS, so we do not provide the warranty for the 3rd party software.

In short, there’s no risk in using Merlin as long as you don’t mess up the firmware migration process or expect tech support from Asus.

How to put Merlin on your Asus router

The good news is flashing your router from Asuswrt to Merlin is the same as upgrading the stock firmware manually. It’s easy enough.

Literally, all you have to do is download the firmware and load it on the router via its web user interface, just like the firmware update process of any standard router.

The following are the steps on an RT-AC88U, which are the same when you use any other Merlin-enabled router.

1. Download the Merlin firmware for your router

Here’s the Merlin firmware link for all supported routers. You want to download the latest Release version, though you can also try the Beta if you want to be adventurous.

The download file comes in the .zip format, which is a compressed folder. You first need to open this file (double click on it) and then get the actual firmware file out. The file you want is named after the router’s model and the firmware version.

Merlin Firmware Extract
It’s easy to extract the firmware file from a ZIP folder. Note the router’s model number in the file name.

In my case, I dragged and dropped the file onto a folder called “Merlin” on my Windows 10 computer’s desktop. The point is you need to remember where you put this firmware file.

2. Login to the router web interface

From a connected computer, log in to the Asus router’s web interface. You can do this by navigating a browser to its default IP address, which is often 192.168.50.1, or router.asus.com.

RT AC88U Firmware Update
On the interface of an Asus router, you can quickly jump to the firmware upgrade section by clicking on the firmware version itself.

You’ll be asked for the username (“admin” by default) and password, which is the one you created when you first set up the router. Once logged in, go to:

Administration -> Firmware Update

Alternatively, you can click on the firmware version at the top of the interface’s webpage to jump to the firmware update section. Now you’re ready to perform the firmware migration in the next step.

3. Upload the Merlin firmware

Click on the Upload button (see screenshot below). A dialog will pop up for you to navigate to the location on the computer that holds the firmware file. In my case, the location is the “Merlin” folder on the desktop, as mentioned above.

RT AC88U Firmware Upload
Navigate to the location of the Merlin firmware file and choose to open it.

Now double click on the Merlin firmware file, or click on it then on Open. The flash process will start immediately.

Important: This process will take a few minutes. During this time, make sure you leave the router and the web interface alone. Don’t unplug the router or the computer from the power!

RT AC88U Firmware Progress
The upgrade/migration process will take a few minutes and needs to be left alone.

After that, the router will restart itself, and the webpage will go back to the login page. Log in to the interface again, and you’ll now see the Merlin logo on the top left corner of the web page. You’re almost there.

asuswrt merlin
The Asuswrt-Merlin logo.

Now manually restart the router one more time by unplugging it from power, wait for a few seconds, then plugging it back in. (You can probably skip this step, but in my experience, a manual restart is always helpful after a firmware change. So do it!)

And that’s it. Mission accomplished.

If, for some reason, you want to switch back to Asuswrt, repeat the steps above, using the router’s stock firmware. Again, either way, the settings will remain.

Merlin firmware: The take away

Everyone will enjoy the better stability Merlin brings to an Asus router. But for the most part, Merlin is a geeky option for advanced users. It opens up a lot of possibilities.

In fact, I know many who only buy an Asus router after Merlin is available for it — and I don’t blame them. If you can appreciate even just one of the many benefits this alternative firmware has to offer, such as the vastly more advanced VPN feature, it’s tough to go back.

One thing is for sure. If you have a supported Asus router that doesn’t work as well as you’d like, putting Merlin on it will, well, magically make it a lot better. Try it. You have nothing to lose.

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20 thoughts on “Got One of These Asus Routers? Sprinkle Some Merlin Magic on It!”

  1. Appreciate the article and am looking to update my Asus RT-AX58U. I do have a second RT-AX58U as a node. It is unclear to me how to update the node first as you indicated. How do I flash the node when I cannot login into it directly?
    Thanks.

    Reply
    • You do that via the router unit’s Interface, Stuart. The step is the same as mentioned in this post, just click on the Upload link of the node (instead of the router.)

      Reply
  2. After reading the forums it looks Like even with Merlin the ASUS routers cannot have more than 16 devices assigned to parental controls or be blockable at any one time.

    I need a great router with a mobile app, vpn client capabilities, and support for many more devices in parental controls that can be blocked by a schedule and by a command or switch. Please point me in the right direction. A more business oriented device is fine if it can do what I need.

    Reply
      • Good morning Dong,

        Thanks for replying. I’m not sure where your thought process lies regarding the MAC address comment. With 4 kids from 7 to 18 in the house, they have a lot of devices in the house to use to create distractions. Computers, laptops, tablets, phones, game systems, VR headsets, the list goes on. And there are some last gen phones, game systems and usb wifi adapters as well. I could get by with a 32 device limit for parental controls, but this information is very hard to find. I’m still not 100% sure what the new limits are for ASUS GT-AX1100. I thought I read that the new generation would support 64 devices in parental controls but now I can’t find that information again. I bought a RT-AX92u under that impression but I was mistaken the limits are still 16.

        Ubiquiti told me there is no limit in their OS but I think you mentioned it was sparcely featured. but they have a mobile app.

        The other feature that is a must is the VPN client which can route selective hosts via the VPN. VPN Fusion from ASUS has worked well, and Merlin has it via Entware on its supported devices.

        If I have to forgo a mobile app to get what I need I will have to, but these other 2 features are a must. Any direction you may have is really appreciated.

        Reply
  3. Great article as usual. I had Merlin on a previous router and would LIKE it on my current AC88U, but I have two AIMesh nodes. It wasn’t clear to me if the nodes will automatically update along with the router or if there are other steps although the article seemed to indicate it works with the nodes. Can you clarify for me?

    Tom

    Reply
      • Ach, I’m probably screwed, my nodes are RP AC-1900 so not supported? How much of a hassle is it, or does it even work, to run Merlin on the router and ASUSWRT on the nodes? IF it worked, one would have to upgrade nodes manually from then on?

        Thanks,
        Tom

        Reply
        • Not much of a hassle to get it work, Tom. And yes, you just need to update the node manually as I mentioned OR revert the router to Asuswrt, update the node, then put Merlin on it again. You can back up the settings and restore before and after. Not that bad.

          Reply
  4. To your point on firmware vs. OS, one note is that Merlin allows you to use Entware which includes 2500+ linux packages easily installable via a package manager (okpg). Hook up a USB drive and you have a credible little Linux box on your hands. Recently I ran across an addon that let’s your run scheduled speed tests (so you can see how slow your cable provider really is…) and includes a nice little UI (https://github.com/jackyaz/spdMerlin).

    Like @ChuckD, I’ve been running it for a while and it has been flawless.

    Reply
    • Thanks for sharing, Jim. Yeap, I’m aware of Entware but just didn’t want to be overwhelmingly geeky and get into a territory that’s very hard to explain in layman’s terms.

      Reply
  5. I ran Merlin on my AC68U for five years or so in a household environment and was very pleased with how it did. I especially liked the fairly frequent updates as they often dealt with security issues.
    Be sure to throw Eric some change too, he’s a dedicated volunteer!

    Reply

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