AC87U Asus Merlin - Jumbo Frames and MTU

[snbnoob]

I'm having an issue setting up Jumbo Frames between my NAS and PC both connected to my AC87U router with the latest Merlin Firmware.

Both the PC and NAS have 9k frames enabled. The router has Jumbo Frames Enabled as well

1. When the PC and NAS are connected directly, 9k packets can be sent and received fine, and i get a 5-10% throughput increase vs a lower MTU.
2. However When the PC and NAS are connected to the router, the max packet caps out at only 3k and performance is lower

I've tried manually setting the LAN MTU in the router to 9k for all interfaces but this doesnt work either.

Any idea what is going on here?

 

[snbnoob]

Anyone able to help?

 

[netware5]

You may want to check if ALL LAN devices (not only router, NAS and PC) support jumbo frames and their network interfaces are properly configured. This is a requirement.

 

[snbnoob]

Thanks for your reply, the only devices physically connected to the router are the NAS and PC.

Would wifi Wii connected devices cause an impact?

Also if i put the NAS and PC behind a switch and then connect that to the router, all works fine.

Its only when i plug the NAS and PC directly into the router that jumbo frames and the packet size fails.

 

[netware5]

Thanks for your reply, the only devices physically connected to the router are the NAS and PC.

Would wifi Wii connected devices cause an impact?

Also if i put the NAS and PC behind a switch and then connect that to the router, all works fine.

Its only when i plug the NAS and PC directly into the router that jumbo frames and the packet size fails.

Wi-Fi connected device have no impact. As everything works fine with switch I think you have a problem with router. Did you tried to experiment with different jumbo frames sizes between standard (1.5k) and maximum (9k)? May be the router has a limit for jumbo frame size, i.e. 3k?

 

[storkinsj]

I would like to figure out if you got this one solved. I don't have the same router hardware but sort of need to make sure this works.

 

[ColinTaylor]

I would like to figure out if you got this one solved. I don't have the same router hardware but sort of need to make sure this works.

What router do you have? What problem are you "sort of" trying to fix?

 

[heysoundude]

I would like to figure out if you got this one solved. I don't have the same router hardware but sort of need to make sure this works.

If you're looking to try to get maximum throughput from your router, you have to take a very broad systemic/network perspective - everything on the network has to support jumbo frames.

Need To Know: Jumbo Frames in Small Networks - SmallNetBuilder

http://forums.smallnetbuilder.com/forumdisplay.php?f=19

www.smallnetbuilder.com

IIRC, you're the guy running a Solana validator? This makes sense in that context. But everybody in that universe needs to be using jumbo frames as well.

 

[storkinsj]

Hi sorry I was just hoping someone had an update. I am not solving yet but short-term-future-proofing.

I am going to be running virtual networking in the house using NSX. So far I have not had to go outside my 10Gbe ethernet switch but I am adding a 3rd computer and in theory I would like the jumbo frames to be able to travel through my AX11000 router no problem.

https://docs.vmware.com/en/VMware-V...UID-3FF2471C-665B-4E84-8DE4-ED3F35A58DE8.html

The default frame size for overlay traffic is oddball- 1700. To make things easier I would likely just bump the frame up to 9000 because that's most likely what gets tested.

I am frequently seeing that "everything on the network must support it" statement. However, I just need to make sure the hypervisors I'm connecting together are able to use that big frame size.

This is something I can work around with wires. But- I just wanted to be clear about what is supported. If 2 ports on my AX11000 were connected to jumbo frame configed NIC's ... and everything else was not, would those two NICs be able to talk to each other with 9000 MTU frames?

I know that routers are mainly used to connect computers to the internet through a WAN that may be 1500 or worse 1492 MTU- and that forcing the router to do translation is a waste for the most part. But I am only interested in connecting a limited number of wired jumbo frame systems together. "Jumbo frame support" is indeed enabled in my merlin LAN settings.

 

[ColinTaylor]

I don't know why the OP was having problems with his RT-AC87U. I suspect it might have been an issue specifically with that model as bizarrely, one of the LAN ports is connected to a separate Realtek chip via a Quantenna SoC. In any case he never returned to post a follow up.

I don't have an AX11000, but 9k jumbo frames work fine on my RT-AC68U and RT-AX86U.

Apparently jumbo frames are not supported by the GT-AX6000.

 

[RMerlin]

Apparently jumbo frames are not supported by the GT-AX6000.

It was recently added by Asus, in 388.

 

[storkinsj]

cool. yes option shows up for me. not sure I have the use case yet but I will try to post back here once I’ve tried the experiment hopefully within the next few weeks