RT-BE88U - 10G speeds are 1G

[vanarebane]

Currently I have set up like this:

From router, SFP+ 10G going to my PC trough fiber.
From router, 10G RJ45 going to my NAS, to ASUS XG-C100C card.
Maximum speeds I get with this are 1G exactly, from PC to NAS.

When I connect NAS to 2.5G, I get 2.5G speeds exactly.
I checked my PC and NAS, and they have MTU of 9000.
The router has no Jumbo Frames settings (it's hidden option, as also mentioned in other thread here)

When I SSH into the router, I see MTU's only 1500 for everything.
The eth0 and eth9, that are the 10G ports, have MTU 1500 and is reported 10G speeds.
With that MTU, I should still expect speeds around 6~7G.
Manually tiring to increase the MTU trough SSH, I get "ifconfig mtu SIOCSIFMTU: Invalid argument", only values up to 1500 are accepted.

I'm not sure why the speed between two 10G ports is just 1G

 

[Squall Leonhart]

sounds like a contact asus situation.

Dong managed nearly 9Gbit out of his review part.

 

[jzchen]

Have you tried turning off Jumbo Packets and testing?

 

[vanarebane]

I just got new RT-BE88U back from RMA (bad WiFi 2.4 radio).

sounds like a contact asus situation.

Dong managed nearly 9Gbit out of his review part.

I did contact ASUS, they are asking almost every detail about the setup to understand the problem.

Have you tried turning off Jumbo Packets and testing?

In my RT-BE88U, the Jumbo Packets are hidden in the admin menu and looks like disabled by default.

In a more in-depth analysis, the problem seems to be with the ASUS XG-C100C v2 NIC card, in the NAS. As it does not like to be bonded and the Proxmox software I'm using, needs to make all networks bonded.
By using iperf3 I now get 1G/9G speed in one direction though. From unRaid (that runs in VM) > Proxmox > RT-BE88U > Fiber to MikroTik CRS305-1G-4S+IN > PC with Mellanox Connectx-3.
But between Proxmox and PC I get 2.5G/2.5G speeds. And between Proxmox and RT-BE88U I get 1G/2.5G

So iperf3 is just limited to the device performance, not networks... so my complaints are invalid here and I'll continue figuring why the PC>NAS is 1G/10G right now.

Thanks for thinking with me here!

 

[jzchen]

Jumbo packets (as I understand) are tricky. Is there a network switch in the middle, and if so does it support the same 9000 packet size?

(As a confession I've never tried SSH and I suspect you have a better understanding than I)....

I just verified on my BE98 Pro WebGUI

Under Advanced Settings -> LAN -> Switch Control (tab) is the Jumbo frame/packet setting

I'd be very surprised if yours does not have it?

It's my understanding that both ends and any configurable switches in between must have the exact same 9000 in order for it to work properly.

 

[vanarebane]

In RT-BE88U, there is only Bonding option (this seems to be setting for 2x LAN to NAS only)

Rest of the options are hidden in HTML. I can manually un-hide them, but not sure if there was a important reason why those options are disabled?

Poking around in SSH, I see that the 10G links are not MTU 9000

And those can't be set to 9000 manually either. So I'd rather look for other reason before breaking the router.

 

[i0ntempest]

Not sure if you've figured it out but I was able to just `nvram set jumbo_frame_enable=1 && reboot` and now MTU on supported interfaces is 10240.

 

[Shonk]

Not sure if you've figured it out but I was able to just `nvram set jumbo_frame_enable=1 && reboot` and now MTU on supported interfaces is 10240.

thanks hope it works on SFP+ i have done it but cant reboot the router for a few hours to test

I really dont understand why its not maxed out from asus already
thats how switches are supposed to be configured its just a setting of the max accepted frame size
it doesnt dictate anything to other devices just if it will or wont accept larger frames

unmanaged switches come maxed

It seems asus added support 2 builds ago
My router was on 3.0.0.6.102_38152 earlier before i upgraded to merlin (it seemed to come up on it from the factory unless it stealth upgraded its self on first boot)
looked in switch control and it wasnt there for me maybe i needed to refresh the page?

ASUS RT-BE88U Firmware version 3.0.0.6.102_38151
version 3.0.0.6.102_38151
2025/04/23
New Features：
1. Added support for Jumbo Frame. This setting can be found under “LAN > Switch Control”.
Bug Fixes and Enhancements：
1. Implemented a security patch to address an OpenVPN issue.
2. Improved compatibility with IoT devices on WPA2/WPA3 networks.
3. Enhanced the stability of remote connections.
4. Resolved an issue with the WiFi scheduler.
5. Improved Parental Control scheduling with support for SDN clients.
6. Fixed an issue causing Movistar IPTV to malfunction.

ASUS RT-BE88U Firmware version 3.0.0.6.102_38152
version 3.0.0.6.102_38152
2025/05/19
Improved system efficiency and stability.
Strengthened input validation and data processing workflows to further enhance security of system.

 

[Shonk]

Can confirm
10Gbps SFP+ LC-LC SM 10KM Optics jumbo frames 9014 works fine 9.92 Gbps Payload (Will be replacing with a 2.5M DAC in a few days)
10Gbps RJ45 port also fine 9.92 Gbps Payload
2.5Gbps ports also fine 2.48 Gbps Payload
1Gbps ports i have no need to test them but presume they are fine

 

[i0ntempest]

thanks hope it works on SFP+ i have done it but cant reboot the router for a few hours to test

I really dont understand why its not maxed out from asus already
thats how switches are supposed to be configured its just a setting of the max accepted frame size
it doesnt dictate anything to other devices just if it will or wont accept larger frames

unmanaged switches come maxed

It seems asus added support 2 builds ago
My router was on 3.0.0.6.102_38152 earlier before i upgraded to merlin (it seemed to come up on it from the factory unless it stealth upgraded its self on first boot)
looked in switch control and it wasnt there for me maybe i needed to refresh the page?

ASUS RT-BE88U Firmware version 3.0.0.6.102_38151
version 3.0.0.6.102_38151
2025/04/23
New Features：
1. Added support for Jumbo Frame. This setting can be found under “LAN > Switch Control”.
Bug Fixes and Enhancements：
1. Implemented a security patch to address an OpenVPN issue.
2. Improved compatibility with IoT devices on WPA2/WPA3 networks.
3. Enhanced the stability of remote connections.
4. Resolved an issue with the WiFi scheduler.
5. Improved Parental Control scheduling with support for SDN clients.
6. Fixed an issue causing Movistar IPTV to malfunction.

ASUS RT-BE88U Firmware version 3.0.0.6.102_38152
version 3.0.0.6.102_38152
2025/05/19
Improved system efficiency and stability.
Strengthened input validation and data processing workflows to further enhance security of system.

If you're using merlin firmware, I believe the latest firmware has not merged 38152 into it yet. I'm also waiting for this (plus the IPv6 DDNS function) to be added.

 

[Shonk]

Yeah i know it's not merged into the merlin webui yet
but didnt notice it in asus firmware i rolled back to asus yesterday for a hour or two
to verify

asus is just using nvram set jumbo_frame_enable=1
which can be confirmed by checking the webui after applying
the nvram value and rebooting

I have also confirmed GT-AX6000 the nvram value works fine
hopefully merlin will add it into LAN - Switch Control for more than just the RT-BE88U