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Asus RT-AC66U 802.11ac router review: Latest firmware makes it a beast

Asus' first 802.11ac router offers great performance with existing Wi-Fi devices and is future-proof thanks to its support of the latest 802.11ac standard.

Dong Ngo SF Labs Manager, Editor / Reviews
CNET editor Dong Ngo has been involved with technology since 2000, starting with testing gadgets and writing code for CNET Labs' benchmarks. He now manages CNET San Francisco Labs, reviews 3D printers, networking/storage devices, and also writes about other topics from online security to new gadgets and how technology impacts the life of people around the world.
Dong Ngo
9 min read

Editors' note: This review was updated on October 30 with the router's rating adjusted to reflect its improvement thanks to a new major firmware update.

Asus RT-AC66U 802.11ac Dual-Band Wireless-AC1750 Gigabit Router

Asus RT-AC66U 802.11ac router

The Good

The <b>Asus RT-AC66U 802.11ac Dual-Band Wireless-AC1750 Gigabit Router</b> offers great performance on the 5GHz frequency band, and lots of features for homes and businesses.

The Bad

The Asus RT-AC66U runs rather hot, and is relatively expensive.

The Bottom Line

The Asus RT-AC66U is an excellent router and is currently one of the best options among those that support the latest 802.11ac Wi-Fi standard.

The RT-AC66U 802.11ac Dual-Band Wireless-AC1750 Gigabit Router is the first wireless router from Asus to support the new 802.11ac Wi-Fi standard. Other than that it's basically the same as the Asus RT-N66U router.

That said, the RT-AC66U offers very fast Wi-Fi on the 5GHz frequency band, both with Wireless-N clients and AC clients. In fact it's the fastest of the few 802.11ac routers currently available on the market. The router also has very good range and its USB ports provide more than just the support for external storage and printers.

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Like the RT-N66U, the RT-AC66U initially suffered from bad firmware and showed terrible performance on the 2.4Ghz band. With the latest update, version, however, the router now much better, offering 2.4Ghz Wi-Fi data rate on bar with other routers of its tiers. The router's latest firmware also brings to life its cloud-based storage features, call AiCloud, which comes in handy for anyone to access/manage their storage remotely.

If you're looking for a top-notch 802.11ac-ready router and don't mind its rather hefty street price of about $190, the RT-AC66U make an excellent choice. Similarly, you can also consider the Netgear R6300.

Design and ease of use
The RT-AC66U looks exactly the same as the RT-N66U with a sleek casing that more resembles a jewelry box than a networking device, though it's still clearly a router due to the detachable external antennas sticking up from its back.

The router is flexible in terms of placement: it can be mounted on the wall, put flat on a surface, or, when coupled with its detachable base, stay in a semivertical position. In any of these positions, the router looks good and rugged, hinting that it's a hard-core networking device.

On the back, (or on top, depending how you set it up), the RT-AC66U has four LAN ports for wired clients and one WAN port to connect to an Internet source, such as a broadband modem. All of these ports are Gigabit Ethernet, meaning you'll also be able to get a fast wired network. In addition to working as a router, the RT-AC66AU can be used as an access point or a media bridge, (you can choose among these roles via its Web interface), and when it's not working as a router, the WAN port can also be used as another LAN port.

Near these ports are the reset button, two USB 2.0 ports, the power button, a tiny power port, and the Wi-Fi Protected Setup (WPS) button, which starts a 2-minute window in which other WPS-enabled clients can enter the wireless network. That's a lot of buttons and ports, but items are distributed well, so it's less cluttered than you would imagine.

On the front, the router has an array of LEDs that show the statuses of the ports on the back, the connection to the Internet, the USB ports, and the wireless networks.

The router comes with a CD of setup software that walks you though every single step, so setting up the router should be very easy for home users. In fact, you'll probably want to skip this CD entirely and use the router's Web interface for the setup process, by pointing a connected computer's browser to, which is the router's default IP address. The first time you go there, the interface will greet you with a Web-based wizard with steps similar to those of the desktop setup software. Using this wizard, you can also quickly choose to use the RT-AC66U as a router, an access point (if you already have a non-wireless router and want to add Wi-Fi to your network), or as a media bridge (in case you want to connect other Ethernet-ready devices to an existing Wi-Fi network.)

No matter how you want to use the RT-AC66U, you're unlikely to run into problems. While it's not the easiest router to set up, if you have some idea about computers, you'll probably get it up and running in just about 10 minutes.

The RT-AC66U's AiCloud feature allows for sharing/streaming not only contents on the connected USB drive but also from connected network clients.

The RT-AC66U's AiCloud feature allows for sharing/streaming not only contents on the connected USB drive but also from connected network clients.

Dong Ngo/CNET

Like all other 802.11ac routers, the Asus RT-AC66U is basically a true dual-band N900 Wireless-N router -- one that simultaneously offers up to 450Mbps Wireless-N standard on each of the two 2.4GHz and 5GHz frequency bands. On top of that, it also supports the latest 802.11ac standard, which is only available on the 5GHz band. This means regardless of what type of Wi-Fi clients you have at home, the RT-AC66U will support them all, and when you get 802.11ac clients, the router will support them, too. In other words, the RT-AC66U offers everything the RT-N66U does, plus 802.11ac.

In addition to the two main Wi-Fi networks, one for each band, the new router also offers up to six guest Wi-Fi networks, three for each band. To turn these networks on (if for some reason you need all of them), you'll need to use the router's Web interface, which is well-organized, responsive, and reasonably simple. At the same time, I found that the interface could still use some improvement, in terms of both features and clarity.

There are three major parts of the interface that you access from the left part of the page. The top part is the Setup wizard, which you can use to rerun the initial setup process; the middle is for General items; and the bottom is the Advanced Settings.

General offers a Network Map for viewing currently connected devices, including those connected to the router via the USB ports. You can click on one of the connected devices to interact with it. For example, you can quickly block a Wi-Fi client or set up a network storage feature of an external hard drive. For the most part this works out very well, but sometimes I found that the router took a long time to register a connected device. This means there could be more connected devices than those displayed on the map.

Also in the General area are other nifty features such as a Parental Control feature, a Traffic Manager, and management of the router's USB ports. The Parental Control feature is very easy to set up; you can quickly add a device to the managed list and quickly pick time slots when these devices can access the Internet. Unfortunately, you can't refine the restriction beyond having or not having access to the Internet. For example, you can't control access to particular Web sites.

The USB ports can be used for a lot of functions. You can connect USB external storage devices or printers to these ports and turn the router into a storage or print server, both of which I found worked well and were easy to set up. With the RT-AC66U, these ports can also be used to host storage over the Internet via a feature called AiDisk, coupled with a cellular USB dongle so the router can work as a mobile hot spot, and when an external hard drive is connected you can also use the router to manage downloads by itself.

The router's PC-less download feature, which didn't work with the router's initial firmware versions, now works as intended in my testing. It supports all type of download services, from regular HTTP downloads to newsgroups to Bit Torrent. The feature can be easily managed via the Web interface and can handle multiple downloads at a time. Unfortunately, in my trials, it couldn't download from sites that require authentication, such as RapidShare. This support might be added via a new version of the download feature or a future firmware update, however.

The router's AiCloud feature, which was also not available before, has, with the latest firmware, become a major feature of the router. AiCloud allows users access to not only sharing/streaming content stored on the connected external drive to iOS and Android mobile devices (or computer via a browser), but also content on the computer connected to the router. This means you can easily share data stored on any computer in the network to remote users. For this feature to work, you need to know how to set up a DynDNS account, which can be done in a few steps within the router's Web interface. I tried this feature out and it proved to be a very handy feature for those with fast Internet connections.

With the latest firmware, the router's PC-less download feature now works, and for the most part works well.

With the latest firmware, the router's PC-less download feature now works, and for the most part works well.

Dong Ngo/CNET

Lastly, the Advanced Settings offer more in-depth access to the router's features, some that would be specifically useful for businesses. The most notable feature is the VPN server for creating a secure virtual private network for remote users. You do need to possess decent networking know-how to set up and manage a VPN. The router also supports IPv6, a customizable firewall, and QoS.

Overall, like the RT-N66U, the RT-AC66U offers many useful features you might want from a high-end router and generally the work very well. Asus says it will continue to update the router's firmware to offer more features and improve the existing ones.

As a 5GHz router the RT-AC66U offered stellar performance, with the fastest data rate I've seen yet. On the 2.4Ghz band, the router wasn't the fastest but still performed decently.

I tested the router with both 802.11ac clients and regular Wireless-N clients. Since there are currently no devices on the market that support 802.11ac, I actually used a second RT-AC66U unit as a media bridge for the 802.11ac Wi-Fi test. At a distance of 15 feet, the Asus registered the fastest Wi-Fi speed I've seen, scoring 339Mbps (or about 42MBps, close to the speed of a Gigabit Ethernet wired connection). At this same distance, when used with a Wireless-N client, the score was also impressive at 208Mbps. When I increased the distance to 100 feet, the router's speed was lowered to 179Mbps and 167Mbps for 802.11ac clients and Wireless-N clients, respectively, still very impressive.

On the 2.4GHz band, where the router works with only Wireless-N clients, it scored only 66Mbps and 50Mbps for the close-range and long-range tests, respectively. These placed the router in the top four in terms of 2.4Ghz data rates. Note that the router was tested at CNET Headquarters in San Francisco, where there are many other Wi-Fi devices, especially on the 2.4GHz band, that might interfere with the router's performance.

In that same environment, the RT-AC66U offered very long range, up to up to 300 feet in my testing. It was also very stable and passed my 48-hour stress test with no problems. During the stress test, the router was set to continuously copy data back and forth between multiple clients, both wireless and wired. Neither of its wireless bands disconnected during this time.

The router offers decent network storage performance, when coupled with an external hard drive, with 134Mbps for writing and 77Mbps for reading over a Gigabit Ethernet connection. These speeds are fast enough for light media streaming and data sharing.

I noted that with the latest firmware, version, the router seemed to be hotter than before during heavy loads. While it wasn't hot enough to be alarming, it should be used in an open space.

CNET Labs 5GHz Wireless-N performance (in Mbps)

(Longer bars indicate better performance)



Asus RT-AC66U (with 802.11ac client)

Netgear R6300 (with 802.11ac client)


AirStation WZR-D1800H (with 802.11ac client)


D-Link DIR-857


Asus RT-AC66U


WD My Net N900 HD


Belkin N900 DB


Cisco Linksys E4200v2


Asus RT-N66U


Netgear R6300


AirStation WZR-D1800H


Netgear WNDR4500


Trendnet TEW-692GR


CNET Labs 2.4GHz Wireless-N performance (in Mbps)

(Longer bars indicate better performance)



Cisco Linksys E4200 v.2

Trendnet TEW-692GR


Netgear WNDR4000


Asus RT-AC66U


WD My Net N900 HD


Asus RT-N66U


Netgear R6300


Belkin N750 DB


D-Link DIR-857


Netgear WNDR4500


Buffalo AirStation WZR-D1800H


Service and support
Asus backs the RT-AC66U with a two-year warranty. At the company's Web site, you'll find downloads, FAQs, a manual, and other support materials. If you want to contact the company's tech support, however, it's better to do that via e-mail as there's no tech-support phone number listed on the Web site.

With great performance and lots of useful features, the Asus RT-AC66U, with the latest firmware, is one of the best 802.11ac-ready routers on the market, worthy of its hefty price tag.

Asus RT-AC66U 802.11ac Dual-Band Wireless-AC1750 Gigabit Router

Asus RT-AC66U 802.11ac router

Score Breakdown

Setup 8Features 9Performance 8