[RT-AX56U] Baffling slower speed via LAN then WiFI

[mara-]

Hello,

I have a really really strange issue. When speed testing my two PC over LAN connected to the RT-AX56U, I get slower speed then testing via phone or via Mac laptop. One of the PC also has integrated WiFi, but it's slow over it too. Here is my setup:

- Huawei E5186s-22a LTE router -> WAN RT-AX56U (Operation Mode:Wireless router, Merlin firmware) -> RT-N12D1 (Operation Mode:Access Point(AP)) -> PC (LAN slower then WiFI)

When I speed test from PC, a get about 40% slower speed then testing via WiFi. But here is the strangest thing.

I also have ADSL connection, and when I plug in ADSL -> WAN RT-AX56U, LAN and WiFI speed are the same.

- Some ZTE ADSL router-> WAN RT-AX56U -> RT-N12D1 -> PC (LAN speed as fast as WiFI)

Speed test also gets good speed when run inside RT-AX56U GUI, same as over WiFi.

The same thing happens on the latest stock Asus firmware. RT-AX56U is connected via static LAN IP to source router (LTE or ADSL) and it's handling DHCP. DHCP is disabled in source router.

Any ideas? I am really puzzled, trying for hours to solve this one.

 

[Tech9]

RT-N12D1

This router doesn't have Gigabit ports - limited to Fast Ethernet or about 94Mbps. No wonder Wi-Fi is faster.

 

[mara-]

Yeah, but it's not reaching it's 100Mbps limit. Over WiFi it's about 50 Mbps, but over LAN it's 30-35Mbps. I also mentioned that one of PC has WiFi 6, and I used 5G WiFi to speed test, and still the same slower speed. Also, if you read my post, none of the issues exist if the source router of the internet is ADSL instead of LTE router.

 

[drinkingbird]

Yeah, but it's not reaching it's 100Mbps limit. Over WiFi it's about 50 Mbps, but over LAN it's 30-35Mbps. I also mentioned that one of PC has WiFi 6, and I used 5G WiFi to speed test, and still the same slower speed. Also, if you read my post, none of the issues exist if the source router of the internet is ADSL instead of LTE router.

What is your ADSL speed? If less than 30-35 megs of course you won't notice a difference as it is below the limit you're hitting when using your faster connection.

Are you sure your wifi is connected to the N AP and not the AX router when you're doing your comparison?

You can check your wiring, maybe the patch cord you're using is bad, or the port in your PC is no good, drivers need updating, etc. Plenty of factors. I'd try another wired device and see if you see the same results. Try doing the same test (wired and wireless) from the AX, at least then you can narrow down which device needs attention.

 

[mara-]

When I test on the PC using WiFi, established connection is 245 Mbps. And still, it can not reach 50Mbps internet speed. The phone can. The thing is, if 4G tower has a higher load, and let's say I measure 25Mbps on the phone, both PC's will go down to 10Mpbs, so it's proportionately worse.

ADSL speed is 30Mbps now, but before it was 40Mpbs, and both PC's could reach those speeds. So, the only issue is when I connect 4G router to WAN RT-AX56U and only with Windows machines, I can not figure out why.

I also tried changing TTL on Windows in case they were limiting something, but it made no difference.

 

[drinkingbird]

When I test on the PC using WiFi, established connection is 245 Mbps. And still, it can not reach 50Mbps internet speed. The phone can. The thing is, if 4G tower has a higher load, and let's say I measure 25Mbps on the phone, both PC's will go down to 10Mpbs, so it's proportionately worse.

ADSL speed is 30Mbps now, but before it was 40Mpbs, and both PC's could reach those speeds. So, the only issue is when I connect 4G router to WAN RT-AX56U and only with Windows machines, I can not figure out why.

I also tried changing TTL on Windows in case they were limiting something, but it made no difference.

Changing the TTL to bypass speed restrictions stopped working for most carriers a long time ago, they figured out that trick. However the TTL on your PC is not learned from the carrier, and since you're behind your own router as far as they know you only have 1 device. It should not be anything to do with them limiting you.

Are you using the same speed test app and server on both phone and PC?

Have you tried testing when connected (both wired and wireless) to the AX router bypassing the other? Need to narrow down where the problem is before you can really start to resolve it. Or even try connecting directly to their router and see what happens.

Windows dynamically adjusts its TCP window size and the higher latency of the cellular connection could be throwing it off too. It may take it a while to learn and adjust. You can disable that and hardcode it just to see if it makes any difference.

 

[mara-]

TCP was a good hint, thanks. I run the command

netsh int tcp set global autotuninglevel=normal

And speed is what I expect it to be now, reaching the same as phone over WiFi. Highest measure was 50/35, same now what I get on the Mac laptop, and the phone. Other PC started getting good speeds without me doing anything, so I figured it must be something with Windows on this PC. So, thanks again for the tip.