Assistance needed with Hardware Acceleration on RT-AC68 and Merlin

[ScooterJM]

Hi All,

I've been running an Asus RT-AC68R for a few years now, with my Xfinity/Comcast cable ISP. I'm running Merlin Firmware 384.3. I love this router and the Merlin firmware.

Recently, I got upgraded to the Xfinity Gigabit (DOCSIS 3.1) service, which advertises up to 1000Mbps down and 35Mpbs upload speed. When connected directly to my modem, I get close to that on the various speed test sites (Xfinity, Speedtest.net and DSLReports) - anywhere from 800-900 download and 30 upload.

However, when connected behind my Asus RT-AC68R, my download speeds slow down considerably, down to 200-300Mbps (I know, cry me a river). I have Cat 5E cabling throughout.

In reading various posts in forums online, I understand this is likely due to hardware acceleration (CTF and FA) being disabled or not optimized in my Asus router.

I have reset my router to default settings, and ensured that QoS is turned off. I've also turned off STP and Jumbo Frames in LAN--> Switch Control. However, I still only see CTF listed next to the NAT Acceleration and on the Tools page it shows "Enabled (CTF only)".

Is anyone else able to get almost full Gigabit download speeds using this router?

Should I see something specifically listed in Tools-> Features showing the hardware acceleration?

Is there a specific hardware version of the AC68 that can not have FA enabled?

What features are incompatible with CTF and FA? Ideally, I'd like to enable VPN and Port Forwarding if I can max my speeds.

Thank you all for any assistance!

 

[modemboy]

Do you have Traffic Analyzer -> Statistic option turned on? That will kill FA as QoS does.

 

[ColinTaylor]

Is there a specific hardware version of the AC68 that can not have FA enabled?

The original RT-AC68U didn't have FA. Later versions of the hardware might have it.

https://www.snbforums.com/threads/r...-fa-nat-acceleration.27611/page-2#post-250193

EDIT: The above statement appears to no longer be true . My "original" RT-AC68U says it has both CTF and FA.

 

[john9527]

Unfortunately, I think ASUS may have mixed and matched processor rev levels across router levels. It's pretty sure that the AC68U-A1 and AC68R don't support FA mode. Other than that, it's a try and see.

There is also a firmware component involved. At least some levels of firmware removed FA mode, even if the processor was capable (I believe due to a conflict with some of the closed source binaries).

 

[ScooterJM]

Unfortunately, I think ASUS may have mixed and matched processor rev levels across router levels. It's pretty sure that the AC68U-A1 and AC68R don't support FA mode. Other than that, it's a try and see.

There is also a firmware component involved. At least some levels of firmware removed FA mode, even if the processor was capable (I believe due to a conflict with some of the closed source binaries).

Interesting - so how do I know which processor rev I have, and if it is capable of FA?

 

[Makaveli]

Interesting - so how do I know which processor rev I have, and if it is capable of FA?

In SSH use this command

cat /proc/cpuinfo

https://www.snbforums.com/threads/how-to-check-cpu-size-rt-68u.30782/

This will show you cpu info not if its FA capable.

 

[ScooterJM]

In SSH use this command

cat /proc/cpuinfo

https://www.snbforums.com/threads/how-to-check-cpu-size-rt-68u.30782/

This will show you cpu info not if its FA capable.

Thanks:

Processor : ARMv7 Processor rev 0 (v7l)

processor : 0

BogoMIPS : 1599.07


processor : 1

BogoMIPS : 1599.07


Features : swp half thumb fastmult edsp

CPU implementer : 0x41

CPU architecture: 7

CPU variant : 0x3

CPU part : 0xc09

CPU revision : 0


Hardware : Northstar Prototype

Revision : 0000

Serial : 0000000000000000

 

[RMerlin]

FA support is not reported by cpuinfo. I don't know how FA support can be queried, Asus's code that does so is closed source, so no idea how they do it.

In general, my advice is not to bother about FA. It's not supported on all models, it even varies between firmware versions, and it's incompatible with many features (more than CTF). CTF alone is sufficient to handle a gigabit Internet connection.

 

[KevTech]

There is also a firmware component involved. At least some levels of firmware removed FA mode, even if the processor was capable (I believe due to a conflict with some of the closed source binaries).

Yes very true as on my RT-AC68U B1 I had CTF and FA but on these latest firmware versions I only have CTF.

I can enable FA again with nvram set ctf_fa_mode=2 but if I reboot the router FA reverts back to disabled.

I just leave FA disabled as I do not really need it.

 

[ScooterJM]

Thank you, RMerlin and KevTech, that is helpful to know. So, if I have CTF enabled, that's good enough! Thanks.

 

[slobodan]

Friend, there is "fake FA". I.e. the router thinks it is FA-capable, but it isn't. In this case enabling FA means slower speeds that CTF alone.

So, yeah, I have a less powerful router, and CTF alone gives me 500 Mbps out of my nominal 500 Mbps download speed.

STP and Jumbo frames do not seem to matter, but any kind of QoS, flow control or censorship cancel the CTF. You may filter all DNS calls to the router itself, that's allowed. You may even do DoH or DoT, that's also allowed.

 

[slobodan]

And let's not forget something less obvious: don't clone your MAC address. It slashes download speed to about 270 Mbps for my router (AC56U).

So, check cloned MAC address in the settings of your router, it has to be empty.

 

[drinkingbird]

AI Protection if enabled will slow you considerably too, so make sure that and traffic analyzer are disabled.

 

[slobodan]

I get 517 Mbps out of nominally 500 Mbps line. I have AI Protection enabled on an AC68U.

 

[Rocketboy235]

Figured I ask here so that all information on what functionality enabled would interfere with hardware acceleration can be in 1 place in case other people stumble upon this thread wanting to know what features affect hardware acceleration...

Would enabling Web History and Bandwidth Monitoring - Apps Analysis under Adaptive QoS affect hardware acceleration as well (not talking about Traffic Analysis - Statistic mentioned earlier)? I know just enabling the regular QoS will affect hardware acceleration but not sure if the other features that can also be found in the Adaptive QoS page can affect hardware acceleration.