Slow (capped) 5Ghz wifi on RT-N66u

[John8oy]

Hi everyone. First post as new to a sus router world.

I've already sent my first router back to Amazon as faulty for a straight exchange. To my dismay the second router is doing the same thing so may point to firmware or configuration issue.
I'm on virgin media 150mbs with superhub 2ac in modem mode. I'm loving the Asus RT-N66U router feature set on the latest Merlin firmware version 3.0.0.4.380.58.
When it's running optimum on my iPhone 6s running Speedtest.net I get 100mbs down / 10mbs up on 2.4Ghz, and 154mbs down / 10mbs up on 5Ghz. The range is good and I get slightly degraded results upstairs but.
Then the fun begins. After a few hours the 5Ghz network will decide to cap itself to 10mbs down / 10mbs up, the 2.4Ghz will still be measuring 100mbs down on speedtest.net.
If I disable the 2.4Ghz band, makes no difference, likewise turning 5Ghz off then on. Also unplugging all lan cables makes no difference likewise repositioning the router and antennas. Sometimes rebooting the router restores normality but not always.
Im now at a loss. I've tried hard resetting router holding down wps button, and evening manually reconfiguring the settings rather than restoring backup. Like I mentioned, this happens on two brand new routers bought from Amazon, first one returned, and I'm on the brink of returning this one unless there some magical setting I've missed. I've never seen this before where it's like a bandwidth cap on just one band and just the downstream, upstream fine, and 2.4Ghz fine.
Anyone shed some light?

Many thanks in advance
John

 

[bbunge]

I've had the best luck with the 378.56_2 build. Ran for almost 6 months with no issues! Am now running the 380.58 build after some initial "issues." Make sure you disconnect any USB drives when you do an upgrade. Use some sort of a WIFI tool to pick the least used chamnnel in your area for both 2.4 and 5 GHZ. Set both to 20 MHZ with a static channel.

 

[Deleted member 22229]

Set both to 20 MHZ with a static channel.

Do NOT set your 5Ghz band to 20 Mhz it completely defeats any reason to even use that band. 5 Ghz on the N66 should be set to 40 Mhz for optimal performance.

 

[John8oy]

Thanks for the reply bbunge. I've tried all the channel setting and site survey. Never had an interference issue in 10 years.
I've just worked out that rebooting the Virgin superhub cable modem seems to rectify. I didn't reboot the Asus. It may be plausible to assume that it's the modem at fault, however wouldn't this also effect the 2.4Ghz band? Throughout the 2.4 remains 100mbs speed from the iPhone. Issue just effects 5Ghz. This becomes more puzzling by the minute.

 

[John8oy]

Ive now re-enabled virgin media super hub as a router, turned off its wireless, and placed Asus in AP mode, so no NAT etc. This is to try troubleshoot if issue lies with modem mode configuration. So far the 5Ghz band has been fine, regularly 150mbs. However, the 2.4Ghz has not capped at 25mbs down, 10mbs up. Very strange!

 

[John8oy]

A full week in access point mode and still seeing evidence that the original wireless speed issue has moved to the 2.4Ghz range. Just run a speedtest.net on iPad and getting 5mbits down, 10mbits up. Switch to 5Ghz and getting full 150mbits down, and full 10 up. Then switch to iPhone, getting full speed on both bands. Test on iPad again and 2.4Ghz still poor. It's like there's Qos running, but it's turn off.
Any ideas anyone? I'm thinking I'm going to have to send this second router back to Amazon and sack Asus all together, maybe go back to a trusty buffalo on DDWRT.

 

[bbunge]

You may want to try the latest firmware from Asus. It is a beta but should work well. Still set the 2.4 to 20 mhz.

Sent from my P01M using Tapatalk

 

[John8oy]

I'll give that a go actually, tried everything else, incl. the merlin John fork which yeilded some issues.

 

[bbunge]

I had an issue with the 380.58 today when I connected a second USB drive. When I tried to download from the drive the N66R shut down hard. I discovered that the drive enclosure was failing and after removing it and rebooting the Asus is humming along fine! As for the 2.4 being set to 20 Mhz, that was a recommendation from Asus tech support. I have a couple of "N" devices that do not like 40 Mhz bandwidth.One HP laptop will quit WIFI within an hour! So I'm happy with the 2.4 at 20 Mhz and the 5 Ghz at 40.

 

[John8oy]

Totally going round in circles here. Tried the Asus beta firmware and still only got 10mbs down on the 5G. gone back to latest Merlin and same issue. Works for a bit on full speed after rebooting router and modem, but then goes back to poor. 10 meg down and 10 meg up using speedtest.net losing will to live!

 

[John8oy]

I've just discovered that if I unplug the lan cable between the RT-N66u and the Superhub 2AC (in modem mode) wait 10 seconds then plug it back in, the 5G optimum download speed is restored. Now getting 150mbs download when run speedtest.net on iphone app?? As opposed to 10mbs What does this suggest?

 

[TonyH]

I've just discovered that if I unplug the lan cable between the RT-N66u and the Superhub 2AC (in modem mode) wait 10 seconds then plug it back in, the 5G optimum download speed is restored. Now getting 150mbs download when run speedtest.net on iphone app?? As opposed to 10mbs What does this suggest?

What is modem mode?

 

[John8oy]

I

What is modem mode?

I'm a uk Virgin media Cable broadband customer, and if you choose to use your own wifi router, you place their supplied router into Modem only mode, with a WAN uplink to your own wifi router.

 

[mstombs]

What 5G channel nos are you using? With same ISP service, but now an SH3 in modem mode, I have had trouble with the higher channel Nos on the N66, I believe this is due to regulatory compliance and 'DFS'. John's fork solves this issue by using old drivers that do not have these channels available! Note that the N66 is cpu-maxed at around 150Mbps with QOS on. I could get >200Mbps wired with QOS off and CTF on with Merlin formware. Without QOS there is always a chance download speeds are limited due to contention on upload. VM service is very asymmetric 150 Mbps service is actually 165 down 10 up. Does pulling the cable just break heavy users connections to allow you to speedtest?

 

[John8oy]

What 5G channel nos are you using? With same ISP service, but now an SH3 in modem mode, I have had trouble with the higher channel Nos on the N66, I believe this is due to regulatory compliance and 'DFS'. John's fork solves this issue by using old drivers that do not have these channels available! Note that the N66 is cpu-maxed at around 150Mbps with QOS on. I could get >200Mbps wired with QOS off and CTF on with Merlin formware. Without QOS there is always a chance download speeds are limited due to contention on upload. VM service is very asymmetric 150 Mbps service is actually 165 down 10 up. Does pulling the cable just break heavy users connections to allow you to speedtest?

I've tried the John's fork and get the same issue. I thought it was a faulty router, so did an exchange with Amazon, but the second router does exactly the same. I get your point that pulling the cable may chop other users, but there was nobody using it at the time. It would have to be a very heavy user to take the bandwidth from 150mbs down to a constant 10mbs. The 2.4ghz side is fine. Just the 5ghz that displays this 'capping' symptom. It seems to be a firmware issue, I don't get any issues with the SuperHub 2ac in router mode. Can some kind of debugging be enabled?

 

[John8oy]

I just thought I update on this issue to confirm it's still an issue. I've just upgraded to latest Merlin firmware released end of sept and this hasn't resolved either. I've now turned off the 5ghz radio because it's getting stuck running at 10meg too often. It's a shame because I needed this for the AppleTV. Apple TV only has 10/100 lan port and runs at only 65meg when the test is run. I'm just stayed studying for a CCNA so hoping to learn a bit more about networking to try solve the issue. I could run wireshark and see what's going on. Does anybody know if Speedtest.net used TCP or UDP? I assume TCP


Sent from my iPhone using Tapatalk

 

[John8oy]

Hi all. I’ve still got this issue. Just decided to do a bit of googling and it’s brought me back to my old post. Virgin media have just replaced my super hub from a 2 to a 3. Placed back in modem mode and with the RT-N66U doing the routing and guess what, yep, after about 2 hours of use my iPad internet speed has dropped from 150mbps down to 10mbps grrrrrrr!!!

Had anyone got any ideas???

Cheers
John

 

[John8oy]

Only fix I have is to unplug the Ethernet uplink from router to superhub wait 10 seconds the plug back in. This restores the speed over 5ghz WiFi back to 150mbps. Could be related to the auto negotiate on the ports. Can anyone help? What about Mr Merlin himself

 

[mstombs]

You do realise that going from the Netgear/Broadcom Superhub 2.0 to the Arris/Intel Hub 3.0 is a downgrade in many respects? Variable latency to the internet, and even pinging the modem from the lan - due to the Bugged Intel Puma Chipset and inadequate DOCSIS specifications and testing.

I'm back using Merlin fw with this combination, IIRC only the lowest 5G channel numbers are any use due to the DFS regulatory issue, haven't noticed a speed issue on 5G. but range not great, I am usually in range of an access point.

 

[ColinTaylor]

@John8oy In the year and a half since you first posted no one else has reported the same problem. This suggests that it is something unique to your setup/environment. Perhaps look for sources of radio interference, like wireless headsets etc.