Question ASUS RT-AC86U limited speed

Ypnos

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Oct 17, 2007
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Hi
I'm at my wit's end with this. I'm in the UK, recently got Virgin Media M500 (500Mbit product). Have to use VM router in modem mode, connected to WAN port of ASUS router.

Good:
Wifi speed tests on 3 mobiles and 2 laptops give a speed test of 550Mbit (more than perfect)
Speedtest built into ASUS router also gives 550Mbit

Bad:
LAN speed limited to 120Mbit on the port. I have tried the following with exact same result:
Plugged directly into router(s)
Tested with desktop PC and 2 laptops
Brand new router (D-Link)!
Tried older TP-Link Archer
CAT5, CAT6 and CAT7 patch leads
Driver updates
Firmware updates on anything with firmware
Also using Devolo Magic 2 adapters (showing 750Mbit link)

Windows control panel shows the ethernet connected at 1Gb, as does Router on the LAN port

Please help!
 

gggplaya

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Check to see if you're double NAT'd by running the TRACERT to 8.8.8.8 in command prompt. If you're double NAT'd, you'll see 2 hops with a Private Address listed. If you're double NAT'd, then your main VM router is not in bridge mode(modem mode).
 

Ypnos

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Oct 17, 2007
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Check to see if you're double NAT'd by running the TRACERT to 8.8.8.8 in command prompt. If you're double NAT'd, you'll see 2 hops with a Private Address listed. If you're double NAT'd, then your main VM router is not in bridge mode(modem mode).
Hi

This is my tracert to 8.8.8.8

1 3 ms 1 ms 1 ms RT-AC86U-E408 [192.168.1.1]
2 * * * Request timed out.
3 10 ms 11 ms 9 ms manc-core-2b-xe-221-0.network.virginmedia.net [62.252.191.177]
4 * * * Request timed out.
5 18 ms 19 ms 15 ms tele-ic-8-ae5-0.network.virginmedia.net [62.252.224.94]
6 19 ms 16 ms 17 ms 72.14.210.114
7 19 ms 19 ms 19 ms 209.85.249.149
8 17 ms 16 ms 17 ms 216.239.58.223
9 17 ms 15 ms 14 ms dns.google [8.8.8.8]
 
I would try to test simple file transfers between 2 machines in your house. Since it is not dependent on your internet speed you should be able to get rates higher than 550. The depends on the disk systems though. You can try a old line mode tool called IPERF. This tests only the networks part and you should see transfer rates between machines at 900+mbps.

This is mostly to see if it is the router causing the issue. Unless the port is physically bad and getting error the router ports act as a simple switch when you go lan-lan.

If you did not say that the wifi worked fine I would suspect that something had disabled the hardware nat acceleration. Normally you factory reset the router and only set the admin and wifi passwords. This makes sure no other feature is on. You can try it but there is not any difference really between lan traffic and wifi traffic internal to the router
 

Ypnos

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Oct 17, 2007
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I would try to test simple file transfers between 2 machines in your house. Since it is not dependent on your internet speed you should be able to get rates higher than 550. The depends on the disk systems though. You can try a old line mode tool called IPERF. This tests only the networks part and you should see transfer rates between machines at 900+mbps.

This is mostly to see if it is the router causing the issue. Unless the port is physically bad and getting error the router ports act as a simple switch when you go lan-lan.

If you did not say that the wifi worked fine I would suspect that something had disabled the hardware nat acceleration. Normally you factory reset the router and only set the admin and wifi passwords. This makes sure no other feature is on. You can try it but there is not any difference really between lan traffic and wifi traffic internal to the router
Hi
I already tried a file transfer between machines on LAN and I get between 120Mbit and 220Mbit. I initially suspected a router fault, but I bought a brand new router (D-Link) and the result was the same...
 
Then the router is a simple switch and not likely the problem.

Try IPERF next and see if you see a problem in the actual network or it is something about the OS. You could also boot a linux USB image and see if your still get limitations. In that case you would suspect some hardware issue if 2 different OS have the same limits.
 

Ypnos

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Now here's a thing. I don't know if this is a red herring, but I've just been into my PC BIOS (Gigabyte Aorus B450) and under the on-board network card it has the speed negotiation. Default setting is Auto, but when I go to manual the only options I have are 10Mbit and 100Mbit (Full and Half duplex). It is definitely a Gigabit card though.
 

Ypnos

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Then the router is a simple switch and not likely the problem.

Try IPERF next and see if you see a problem in the actual network or it is something about the OS. You could also boot a linux USB image and see if your still get limitations. In that case you would suspect some hardware issue if 2 different OS have the same limits.
I've downlaoded iperf3 and there's a myriad of switches. Do I need to run something specific?

OK I ran a few iperf commands, I am getting a very steady 115Mbit transfers. Even tried the Android app and I'm getting the exact same numbers.
 
Last edited:

Ypnos

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If you did not say that the wifi worked fine I would suspect that something had disabled the hardware nat acceleration.
I thought you might be on to something here. ASUS doesn't allow mere mortals to change NAT acceleration, so I installed Merlin WRT that does and even with hw acceleration I get the same results.

Under Hardware Acceleration I have Runner: Enabled and Flow Cache: Enabled
 

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