Asus RT-AC66U Dual-band Gigabit DD-WRT Router review

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We received this amazing router flashed with DD-WRT from FlashRouters and while initially we had some problems with optimising it and speed pass troughs, overall we were very impressed with this router.

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Price: $349.95 (new)

Frequency bands: Dual, 2.4 GHz and 5 GHz (simultaneous)

Wireless standards: IEEE 802.11 a/c b/g/n

Wireless data rate: AC1750 (450+1300Mbps)

Ports: 4 x Gigabit Ethernet (10/100/1000Mbps), 1 x WAN, 2 x USB 2.0

Antenna Type: 3 x external

Processor speed: 600 MHz

Memory: 256 MB RAM, 128 MB Flash

(Full specs available here)

The Asus RT-AC66U is something of a beast, and will do pretty much everything you might possibly want from a router. It supports the new (faster) 802.11ac wireless standard, and can broadcast simultaneously on both the standard 2.4GHz frequency, and on the less busy (and therefore subject to less interference) 5 GHz one, with wireless transfer speeds reaching up to an impressive 1.75Gbs.

New smart phones and tablets usually support both 802.11ac and 5GHz, while computers can be easily upgraded with a USB dongle, while older tablets and phones will have to make do with 802.1n and the 2.4GHz frequency range. Alternatively, the four Gigabit Ethernet ports will ensure blindingly fast transfer speeds for wired connections.

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Internet speeds are of course limited by your broadband availability and/or package, but with this router you can shuffle files around your home or office LAN ridiculously fast., and if you are lucky enough to have ‘super broadband’ access,  then that will also benefit from the RT-AC66U’s super-fast connectivity.

The RT-AC66U comes equipped with two USB ports, which allow you connect hard drives for use as NAS (Network Attached storage) devices, so all your family or office members can easily access and stream a shared pool of files from anywhere within range of the router. You can also attach a printer, so that it can be wirelessly shared by everyone in range


With its three independently adjustable external antennas (which can also be removed or replaced with higher gain alternatives should you wish), the RT-AC66U certainly looks distinctive. Whether the antennas add to the router’s otherwise smart looks is debatable, but it should help ensure great coverage.

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Getting the best coverage involves twiddling around with positioning the router, the antennas, and playing with frequency bands (the inSSIDer program is useful for this), but it is probably be worth the effort to get the best out of your router.

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The router can be mounted vertically with the included stand, or wall mounted out of the way.


Setup is ridiculously easy – basically just plug the router into your broadband modem, turn it and on, and you are good to go.  The first thing you should do once you have connected a computer, is head to the router configuration page (type into your internet browser) and change the network names and passwords.

SSID setup
Note that because this is dual-and router you can effectively run to two separate networks out of the same router. This means that you will of course have to setup names and passwords for both networks.

FlashRouter’s supplied configuration guide is text-only, but gently holds your hand through the process.

Out of the box performance

To get a basic idea of what the RT-AC66U can do, we tested it before configuring VPN.

We have a 20MB/s UK broadband connection, and our PC is only capable of picking up a 2.4GHz. 802.11n signal. The router was connected to a Netgear VMDG280 Wireless N modem/router supplied by our ISP, Virgin Media.

st none

tbb none
Connected directly to our home modem/router (i.e. not connected to the RT-ACU66U)

 st oob

tbb oob
Connected to the RT-ACU66U

802.11ac/ 5GHz performance

Although our PC connection can’t handle the latest WiFi standards, we have Samsung Galaxy S4 phone that can…

mobst none
Connected directly to our home modem/router (i.e. not connected to the RT-ACU66U)

mobst oob UK
Connected to the RT-ACU66U

Note that results varied a little, but the RT-ACU66U results were much more consistent than on our stock router/modem, and are clearly maxing out our 20 meg internet connection.

As far as range goes we wandered around our building, phone in hand, and noted what reception was like at different ranges / positions in the building. Not very scientific, but it’s the best we can do, and to honest we were a little disappointed with the results. 2.4Ghz coverage more or less matched that of our stock ISP supplied router/modem, and while 5 GHz coverage was a little better, it was not by much. We have heard great things about the RT-ACU66U’s coverage, so we are a little surprised at this, although as noted earlier, fiddling around with antenna positioning, and frequency bands etc. is likely to produce improved results.

Edit: Flashrouters contacted us to say that we should have used N-Only on one of the Wireless Network Modes, ‘as Mixed mode maxes out speeds at Wireless-G, hindering the overall range and performance’.

wireless n

Well, this is learning process for us, so we followed the suggestion, and ran some tests to see what difference it made. To do this, we used a program called LAN Speed Test on our (2.4 MHz N-capable only) Windows PC. The test measured the transfer speeds of 10 x 100MB file packets.

LAN test PC 100MB default
When connected to our stock router/modem

LAN test PC 100MB router
When connected to RT-AC66U

As you can see, there is a definite speed bump when using the RT-AC66U, which should when doing things such as streaming video content over the network.

Note that we did also try to test  WiFi speeds using our 5GHz AC-capable phone (connected using AC-Only), but the result were too unreliable to publish. We did however notice a slight range increase when using both N-Only and AC-Only, over when using the ‘Mixed’ setting.


VPN performance is an area that we are obviously very interested in, and setup using the DD-WRT built-in VPN client was very easy (unlike with the N300, where we needed to use a workaround). Note that DD-WRT supports both the PPTP and OpenVPN protocols, but as PPTP is highly insecure, we will consider only OpenVPN.

vpn client

We tested VPN performance on one of PIA’s UK servers:

 st vpn router uk

tbb router
With VPN on router

 st vpn soft uk
tbb soft
Using same VPN and test servers with VPN software client

Given that the tbbMeter download results more accurately reflects real-world performance than the Flash based speedtest ones (and the results were quite close on that test anyway), the router performs as well, if not better than the software client. This is great, as a big problem with consumer grade routers is that their limited computing power cannot cope with processing needed for VPN, resulting in poor performance (see our N300 review). Thankfully the RT-ACU66U is more than up for the job.


The RT-ACU66U is fantastic router, and one of the very best available on the market. It has to be said that ‘off-the shelf’, it comes with some very good software (including a VPN client, albeit one that is PPTP and L2TP only), but by going down the DD-WRT route you gain access to the full range of the hardware’s capabilities.

We were a little surprised and disappointed with a lack of marked improvement in range when using the RT-ACU66U, although given that many have praised the router on this front it may just be our building to blame. In all other respects though, it is an amazing bit of kit – broadcasting two separate networks for high speed file transfers among as many users as you can throw at it, allowing hard drive storage and a printer resources to be wirelessly shared, and providing excellent OpenVPN performance. As far as we know, there is no better router out there.

Douglas Crawford I am a freelance writer, technology enthusiast, and lover of life who enjoys spinning words and sharing knowledge for a living. Find me on Google+

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6 responses to “Asus RT-AC66U Dual-band Gigabit DD-WRT Router review

    1. Hi Hippo,

      The RT-ACU66U remains a great router, and is still one that I use. I have not recently performed a full survey of routers currently available, so I’m afraid that I cannot definitively answer your question. I have, however, been provided with high-end Lynksys WRT-1200 AC rtouter by ExpressVPN, which I intend to review this week. So the results should be interesting.

  1. Thanks again for an objective review. I have just bought the ASUS AC56U which has similar specs I believe.

    I was going to put DD-WRT on it but I stumbled across the ASUSwrt Merlin software which is opensource built on top of a Tomato base. It actually offers a number of features such as OpenVPN. Maybe not as many features but probably a lot more stable as it is specific to ASUS hardware. May be worth considering for some?

    1. Hi Adam,

      Sounds interesting, and definitely worth considering. The only thing I will note is that I have used this very Asus RT-AC66U router with DD-WRT since I wrote this review, and have never encountered any stability issues.

  2. “but by going down the DD-WRT route you gain access to the full range of the hardware’s capabilities.”
    I must say you are a bit wrong there, it seems like with dd-wrt we are missing some HW acceleration on high speed connections:
    – with stock firmware I’m able to dowload up to 200mbps with 5G (ac) wifi
    – with dd-wrt I can’t do better than 100mbps with 5G (ac) wifi + sometimes it gets even impossible to connect to the 5G wifi…

    so I guess as long as your internet connection is slow dd-wrt will make it. But with fiber or Docsis 3.1 you might rather keep the stock firmware or try merlin’s asuswrt custom firmware.

    1. Hi Ayman,

      That is interesting, thanks. I have only a 20Mb/s second connection (and also did not have a stock router to compare the DD-WRT one with), and so did not encounter this issue. It does however make sense that the stock firmware, which is custom-made for the router, may be better able to squeeze every last drop of performance out of it. Nevertheless, I think for most users this will never be an issue, and is compensated for the flexibility of DD-WRT.

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