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RT-AX88U slow LAN speed

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markc

New Around Here
I just installed merlin 384.18 on a RT-AX88U hoping to get full 1GB LAN speed compared to the stock firmware. When using NFS to a HP Microserver via a dedicated 1GB switch I would often get just over 100MBytes when copying large files from my laptop to the HP NAS. When I swap the AX88U in (all else being the same) that speed drops down to 70-80 MBytes and if I try Jumbo frames it goes down to 40-50 MBytes. I've followed quite a few google results and disabled QoS and IPv6 among other things. I'm not concerned about WAN speed because I only have 100Mbs cable. I know there are a lot of possible variables involved but would anyone that currently gets the full 100+ MBytes local LAN transfer speeds care to give some hints on how they have configured their AX88U, please?
 
Do you have CTF enabled (NAT Acceleration) under LAN - > Switch Control?

2020-08-03 07_23_09-ASUS Wireless Router RT-AC88U - Switch Control.png
 
I get full lan speeds and my setup is pretty default.

What is the I/O on both ends of the transfer?

HDD's SSDs?

 
I also have this problem. I was getting full 1.0gbps speed over a wired connection on stock firmware, switched to Merlin and ran the speedtest again before making any changes and my speed was halved to 400-500mbps. I then switched back to stock and am still stuck at half speed.

Per sbsnb's suggestion to check CTF, I don't have that setting in stock. Could switching to Merlin have enabled CTF and left it enabled when I switched back to stock, I just don't have the UI element to see it now?

1596475445066.png
 
@Trav06 when switching back and forth between RMerlin and stock Asus firmware, a full reset to factory defaults is required. Followed by a minimal and manual configuration of the router to secure it and connect to your ISP. Do not use any saved backup config files that were not created 'clean' on the firmware and hardware you want to restore them to.
 
@Trav06 when switching back and forth between RMerlin and stock Asus firmware, a full reset to factory defaults is required. Followed by a minimal and manual configuration of the router to secure it and connect to your ISP. Do not use any saved backup config files that were not created 'clean' on the firmware and hardware you want to restore them to.
Required, meaning automatically done as a part of the firmware install, or meaning I should have selected an option to do a full factory reset?
 
Required, meaning you need to initiate it.


See the last couple of paragraphs in the link above to do it 'once' and properly. :)
 
Thanks @L&LD! With my family stuck at home relying on this network I've been trying to avoid taking it down for any longer than necessary. Everything works at the moment, but at least I know now that if I want to fix my wired speed there's not a shortcut. :)

I'll hang onto these guides for when I'm ready to fix it.
 
I know the feeling. If it's something that has to be done and I can't do it when they're sleeping, I usually just tell them the internet will be down for ~1 hour tomorrow at 3 o'clock or something. If it's a planned outage I don't get too much push back.
 
Hi everyone,

I have just upgraded my broadband to Full Fiber 900. My problem is that on the LAN I cannot get the same speeds as on the router.

Internet Speed 1 - router.JPG


Download test done directly on the router:

wget https://mirror.init7.net/ubuntu-releases/trusty/ubuntu-14.04.6-desktop-amd64.iso
--2022-10-10 16:55:08-- https://mirror.init7.net/ubuntu-releases/trusty/ubuntu-14.04.6-desktop-amd64.iso
Resolving mirror.init7.net... 109.202.202.202, 2001:1620::1620
Connecting to mirror.init7.net|109.202.202.202|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 1157627904 (1.1G) [application/octet-stream]
Saving to: 'ubuntu-14.04.6-desktop-amd64.iso'
ubuntu-14.04.6-desktop-amd64.iso 39%[=============================================================================> ] 439.37M 102MB/s in 4.5s

Connection speed test on the computer connected directly to the router:

Internet Speed 2 - LAN PC.JPG


AX88U-Switch-control.jpg


Adaptive QoS -> QoS -> OFF
Traffic Analyzer -> Statistic -> OFF
Tools -> Sysinfo -> Hardware Acceleration -> Runner and Flow Cache are both listed as Enabled

Could you please advise.

Thank you in advance.
 
Last edited:
Hi everyone,

I have just upgraded my broadband to Full Fiber 900. My problem is that on the LAN I cannot get the same speeds as on the router.

View attachment 44730

Download test done directly on the router:



Connection speed test on the computer connected directly to the router:

View attachment 44731

View attachment 44732

Adaptive QoS -> QoS -> OFF
Traffic Analyzer -> Statistic -> OFF
Tools -> Sysinfo -> Hardware Acceleration -> Runner and Flow Cache are both listed as Enabled

Could you please advise.

Thank you in advance.

Sounds like your client may be the issue. Have you updated drivers etc? While the speed test is running is your client CPU at 100%?

Is all QOS (not just adaptive) disabled in the router?
 
Sounds like your client may be the issue. Have you updated drivers etc? While the speed test is running is your client CPU at 100%?

Is all QOS (not just adaptive) disabled in the router?
Hi,

I have tried on different devices connected with different LAN cables - same issue.
I don't QoS enabled

I have just done another speed test now and the CPU was < 60%

I have better speed on devices connected on WiFi than on LAN.

Thanks.
 
Hi,

I have tried on different devices connected with different LAN cables - same issue.
I don't QoS enabled

I have just done another speed test now and the CPU was < 60%

I have better speed on devices connected on WiFi than on LAN.

Thanks.
CPU on the router or client? Check both.

If neither is pegged, maybe an issue with your wiring? Have you tried different patch cables?

Make sure none of your clients are hardcoded speed or duplex. They should be auto/auto.

If you can get 1 gig LAN to LAN but not to WAN and the router CPU isn't pegged, only suggestion I have is factory defaults, test with minimal config, and add features back in one by one.
 
Hi guys. I having trouble with my router and i found this threat. I am an AX88U owner with the latest Marlinwrt version 388.1. Recently i updated my ISP speed to 300Mbps/30Mbps. The previous program was 100/30 and i have no issue as my router speedtest was 103/32 and my PC speedtest was 95/30 connect with cable from LAN1 router port. With the Updated provider program, my router speedtest is 308/34 but my PC speedtest is again 95/30.

The UTP cable is cat 5e that can afford the speed. My PC card is 1Gbit and set correctly. I install the ASUS firmware and did a hard reset with the onboard button but nothing changed. The WIFI devices speedtest is almost 300/30. I search all the web and cant find any solution. In the router settings it says for LAN1,2,3 ports that the max speed is 100Mbps but i cant change this anywhere (attached photo). I disable airmesh, Qos and all the above you mention.

Hope for your help.
 

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Make sure your PC's network adapter's speed is set to "auto". Did you make the cables yourself. It's possible you mis-wired them.

Try moving the three LAN devices from ports 1-3 to ports 6-8 and see if that makes a difference.

If there's no change try a hard reset: https://www.asus.com/support/FAQ/1039078
 
Last edited:
Colin thanks for your response. My network adapter speed is set to auto, although i check and with 1Gbit full with no result. The cable is ok i test it with a cable tester and can afford speeds up to 1Gbit. I will try and the other lan ports and let you know.
 
Colin thanks for your response. My network adapter speed is set to auto, although i check and with 1Gbit full with no result. The cable is ok i test it with a cable tester and can afford speeds up to 1Gbit. I will try and the other lan ports and let you know.

Unless you have a really nice fluke cable tester it won't tell you that it can do 1G speed, only that it has all 8 wires.

The main reason for not being able to negotiate gig is a pinout/wiring problem (100M is only pins 1/2/3/6, gig uses all 8). Could be a bad port on the router or something stuck in the port, but test with another cable and port (as Colin mentioned) to try and narrow it down.
 
I feel a little dump today. Yesterday i spend 2 hours trying to solve my problem with the speed and today i woke up and the problem solved in my mind immediately.
Somewhere in my installation i have a switch and guess........the switch was 100Mpbs max speed. Today i install a new one and everything works like a charm. Thank you guys for your fast response. Hope this topic help other in the future.
 
Somewhere in my installation i have a switch and guess........the switch was 100Mpbs max speed. Today i install a new one and everything works like a charm.
That's rather still confusing. In my original reply I wrote asking whether you were using an intermediate switch. However I removed that question because your screenshot shows three LAN devices at 100Mbps. So do you have three switches, or one switch and two 100Mbps devices?
 

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