Troubleshooting Slow LAN Speed on RT-AC68U

[pjd50]

Hello,

I have Xfinity Gigabyte internet service, with a Netgear CMV1150V modem. I have an RT-AC68U Router on the latest firmware (384.15). Unfortunately, I have found that using the Netgear cuts my LAN ethernet internet speed by about 80%.

I have a newer PC (with a nice Gigabit ethernet port). When I connect via a CAT6A cable directly to the modem, I get expected speeds in the 900MBps DL and 40MBps UL. As soon as I use I connect the modem to the router via an ethernet cable, and from my PC to the router my speed falls to about ~200MBps.

I have tried to minimize variables to troubleshoot the problem (such as using the same Ethernet CAT6A cable hooked into the back of the PC) - and the speed is only slow when connected to the router. I've tried using different ethernet cables and also making sure that the all the connections were firmly placed. No luck.

It seems this isn't an isolated issue, I found the following while trying to fix my problem:

1. https://forums.tomshardware.com/threads/asus-rt-ac88u-slow-ethernet-speeds.3178195/
2. https://www.reddit.com/r/HomeNetworking/comments/3hw9a2/asus_rtac68u_slow_lan_speeds/
3. https://www.reddit.com/r/HomeNetworking/comments/78qxae/asus_rtac68u_slow_cable_speed/
4. https://www.snbforums.com/threads/rt-ac68u-slow-lan-speeds-both-wired-and-wireless.42564/
5. https://www.bleepingcomputer.com/forums/t/622949/asus-rt-ac68u-ethernet-ports-very-slow/

Among others.

From searching, people had recommended the following:

1. Turning off QoS (this was already off)
2. Enabling jumbo packets (I enabled, and got no improvement in speed)
3. I also tried changing "NAT acceleration" and had no improvement.

I really like the RT-AC68U, but the speed drop is disappointing as I am paying for Gigabit tier service and have several devices and enjoy streaming HD content.

Has anyone successfully navigated this problem? I am happy to provide logs or anything else requested that may solve this problem. I tried to solve it myself, but besides "turning of QoS magically solved all my issues" (which was not applicable in my case, as it was already turned off) I didn't find any success.

 

[Grisu]

Nat acceleration should do it, did you restart (power off) after changing this setting?

 

[pjd50]

Nat acceleration should do it, did you restart (power off) after changing this setting?

Turned of NAT acceleration and then did a hard power-off after changing the setting - no change/improvement.

Any other things to try/troubleshoot?

 

[pjd50]

Turned of NAT acceleration and then did a hard power-off after changing the setting - no change/improvement.

Any other things to try/troubleshoot?

This link suggests it might be an issue with the firmware (thought he points it was primarily because of a WiFi issue on 2.4GHz) - does this help pinpoint the problem?

https://www.privateinternetaccess.c...s-rt-ac68-router-with-merlin-firmware-updated

 

[Grisu]

It should be turned on, not off.
Test with some older firmwares, can be a firmware issue too.

 

[pjd50]

It should be turned on, not off.
Test with some older firmwares, can be a firmware issue too.

Thanks for the clarification. Any recommendations on an older firmware to look into?

 

[Grisu]

384.14, .13_2 and .12

 

[pjd50]

384.14, .13_2 and .12

Tried these firmware versions without success.

I came across this post: https://www.privateinternetaccess.c...s-rt-ac68-router-with-merlin-firmware-updated

which showed some users had success with 380.57 (though with NAT off?).

I tried 380.57 and did see a speed increase (to 266.87 MBps), while everything in the 384's all got me speeds in the 190 MBps.

Anything else I can try to get maximum speed from the router? Is there any other setting I can work with? How about with the CM1150V modem? I know that when I power cycle the modem and direct connect to a PC, I get speeds in the 950-980 MBps - perhaps there is a setting on the modem to tell it that it is communicating with a router, not a PC?

 

[pjd50]

Tried these firmware versions without success.

I came across this post: https://www.privateinternetaccess.c...s-rt-ac68-router-with-merlin-firmware-updated

which showed some users had success with 380.57 (though with NAT off?).

I tried 380.57 and did see a speed increase (to 266.87 MBps), while everything in the 384's all got me speeds in the 190 MBps.

Anything else I can try to get maximum speed from the router? Is there any other setting I can work with? How about with the CM1150V modem? I know that when I power cycle the modem and direct connect to a PC, I get speeds in the 950-980 MBps - perhaps there is a setting on the modem to tell it that it is communicating with a router, not a PC?

Also, I'm not sure if this helps with the diagnosis, but the wireless speed (using devices with fast wireless chips, e.g. iPhone 11 Pro Max), also cap out at about 190 MBps.

So both the LAN and the WiFi speeds are cut down to the 200 MBps speed.

 

[pjd50]

There is a lot of discussion on this issue here: https://www.snbforums.com/threads/performance-issue-with-1-gigabit-an-router-rt-ac68u.41562/

1. Tried turning on/off NAT acceleration - no change
2. Disabled/Enabled Spanning-Tree Protocol (STP) - no change
3. Tried disabling asusnat tunnel under Tools, Other settings, almost at the bottom - no change

I'm out of things to try at this point? Do I need to upgrade to a new router?

 

[ColinTaylor]

So what does it say at Tools > System Information > Network > HW acceleration

What is your WAN Connection Type set to?

 

[pjd50]

So what does it say at Tools > System Information > Network > HW acceleration

What is your WAN Connection Type set to?

Enabled (CTF + FA)


However, after some trial and error, I think I got everything working (or at least working well enough, into the high 800 MBps). I did a "hard reset" (NVRAM reset) on the router. I thought I did this before and didn't have much luck, but either this time was successful (or I am misremembering) - but "nuking" all the settings and starting from square 1 seems to have mostly resolved the issue.

 

[Val D.]

but "nuking" all the settings and starting from square 1 seems to have mostly resolved the issue.

About wireless speed: You never mentioned your 5GHz radio WiFi settings. If you leave them on Auto, the "issue" may happen again. If the router senses increased noise levels and interference, it may switch between 20-40-80MHz wide 5GHz channel and as a result you'll see again what you describe above. It shouldn't be affecting LAN throughput, though. Wireless only.

 

[dlandiss]

I think I got everything working (or at least working well enough, into the high 800 MBps).

That sounds unlikely to me. 800MBps (Mega Bytes per second) translates to 6400Mbps (Mega bits) or 6.4Gbps, about six times the capacity of a typical home LAN.

 

[OzarkEdge]

That sounds unlikely to me. 800MBps (Mega Bytes per second) translates to 6400Mbps (Mega bits) or 6.4Gbps, about six times the capacity of a typical home LAN.

Ah... the Show Me state! I know it well.

OE

 

[KGB7]

Enabled (CTF + FA)


However, after some trial and error, I think I got everything working (or at least working well enough, into the high 800 MBps). I did a "hard reset" (NVRAM reset) on the router. I thought I did this before and didn't have much luck, but either this time was successful (or I am misremembering) - but "nuking" all the settings and starting from square 1 seems to have mostly resolved the issue.

Years ago, and I don't mean to sound like a grandpa. It was daily recommended here on the forums, not sure why its no longer recommended anymore, or perhaps its has been forgotten.

So the steps to fix many issues were; Reset router, flash firmware, let router fully boot. Reset router again, flash firmware again, reset router again...setup router with your settings.

These steps used to be recommended, because old settings or codes would get stuck sometimes in the routers flash chip. But firmware and its code got better over time and no longer requires such drastic steps?? But such drastic steps still work, because nothing is perfect.

A hard reset after every firmware flash, IMHO is highly recommend. It should be written in every bible that you find in a night stand at every motel.

Reset, flash, reset, flash. Setup.

 

[Val D.]

These steps used to be recommended, because old settings or codes would get stuck sometimes in the routers flash chip.

Stuck in the flash chip? Interesting chips those manufacturers use.

 

[L&LD]

An M&M Config and the Nuclear reset is basically what you're describing. Still recommended when network issues include bugs/gremlins that seemingly (almost) no other user has reported.

See my link in the signature below for those and other guides to get your router/network to a good/known state.

 

[KGB7]

Stuck in the flash chip? Interesting chips those manufacturers use.

Listen here smarty pants! I might not remember exact technical lingo from 6 years, but I can still tie my shoes.

 

[KGB7]

An M&M Config and the Nuclear reset is basically what you're describing. Still recommended when network issues include bugs/gremlins that seemingly (almost) no other user has reported.

See my link in the signature below for those and other guides to get your router/network to a good/known state.

Just looked at your M&M guide. Good guide.

Buuuut.... in the past, reusing saved config file, at times re-introduced same issues. A good practice, is take a screen shot of everything and input everything manually from scratch.


Maybe things have changed over time, as firmware has improved??