MTU 1500 limit

[BrimoXD99]

Few days ago I replaced Orange Funbox 6 with ONT LEOX LXT-010H-D
Configuration in Asus RT-AX88U done, internet connection established.
Every 30 minutes running spdMerlin.
With Funbox it is constant 630 Mb/s +/- 2-3 Mb/s
With ONT Leox in between 577 Mb/s and 630 Mb/s
Original MTU in Funbox is 1540.
In Asus it is possible to select MTU = 1500 max so I set this 1500 and the result is as mentioned: in between 577 Mb/s and 630 Mb/s
When I changed MTU to default 1492 results are even much worst: 380 - 560 Mb/s

Conclusion seems to be simple: MTU lower value = worst internet connection stability and speed.

Why there is a limit in MTU = 1500 in Asus MerlinWRT?

 

[RMerlin]

Why there is a limit in MTU = 1500 in Asus MerlinWRT?

Because this is the standard MTU used by Ethernet.

 

[BrimoXD99]

Is there any chance in next firmware release for bigger value, like 1540 in Funbox 6 router?

 

[RMerlin]

Is there any chance in next firmware release for bigger value, like 1540 in Funbox 6 router?

No.

 

[BrimoXD99]

Of course.
How could I even think about an extension like higher MTU if you can't even fix the broken Time Scheduling or LED control issue.

 

[RMerlin]

LED control: closed source code. Beside it works fine for me on the three separate models I tested it on.
Supporting larger MTU: requires access to the low level documentation for every individual switch supported by all 20+ models, only Asus has that documentation. The switch need to be configured to accept non standard MTUs.
Time Scheduling: Asus is constantly making extensive changes to that code, so it's up to them to fix it.

If you think all of these are easy, then you are welcome to submit a pull request with actual patches.

 

[sfx2000]

Supporting larger MTU: requires access to the low level documentation for every individual switch supported by all 20+ models, only Asus has that documentation. The switch need to be configured to accept non standard MTUs.

Exactly - AsusWRT supports more than just Broadcom across different vendor SDK's - they support multiple vendors as well..

On the WAN/LAN interface, the MTU 1500 is standard - there are options to reduce this for things like PPoE and 5G on the WAN side.