Archer C7v5 - Help optimizing WAN Speed over PPPoe and VLAN

[EDIT] Original title was: Archer C7v5 - Force Wan speed to 1000Mbps but I realized my issue was with the C7's CPU and optimization after a while...
[/EDIT]

Hello there, new OpenWrt user here!
I have read dozens of posts on the forum on the subject but could not find a suitable answer (referring to old method that don't work anymore)

Here is the issue: The ONT from my Gigabit fiber Internet provider has a bug that will not make it negotiate the speed correctly and will default to 100Mbps between it and the router.
In the stock firmware, there was a menu entry where I could force 1000Mbps and disable auto-negociation. The ONT was responding correctly to that.

I can't find a similar option in openWrt (luci) and my attempts to do it through ssh have failed because the packages are no longer up to date to support these functionalities.

Can someone point me to a correct procedure to force the WAN port to 1000Gbps without auto-negociation?

Side node: the ONT uses PPPoe behind a V-LAN if this makes any difference in the procedure.

I just made some progress, but not all the way through...
I had speeds a little over 100mbps this morning, which made me realize I miss-diagnosed the issue... (the 100mbps auto-negotiation was a real issue with the original firmware)

I enabled flow offloading, but it did not get me speeds as fast as what the stock firmware was capable of...
(stock firmware is around 900mbps up/down, OpwnWrt with flow offloading 230down 380 up)

What can I do to make the router go faster on OpenWRT ?

Edit: I checked CPU usage with the top command and while doing a speed test, it is 100% even with hardware offloading on... SO there might be some unnecessary computing hapening... Can someone help me with the firewall settings to optimize this?

Some more tests proved that the hardware offloading for switching works great as LAN to LAN speed is around 940Mbps, so basically gigabit...

What baffles me is that using a similar setup on stock firmware gets me really good performance over WAN... but not in OpenWrt...

I reverted to the stock firmware... Speeds are back in the 8-900mbps range on WAN and saturate my Wifi links...

Waiting for some openWRT gurus out there to give me some insight :slight_smile:

Around 200 MBit/s is the maximum this decade old hardware can do, software flow-offloading might make it appear to do 400-500 MBit/s; routing 1 GBit/s needs considerable faster hardware.

Thank you for this... but it does not explain why on stock firmware it is capable of 3x more performance than on OpenWrt

Also, the V5 is not that old and has revised hardware (came out around 2018 in America)...
I have seen posts on the forum with people getting similar performance to the stock firmware, but no explanation on how they achieved it...

I will keep digging a bit and keep you people posted... Maybe offloading PPPoe to another device or something similar...

Software Offloading is buggy in Archer c7 v5 , check this fix at the end of the thread.

or you can try last 21.x stable openwrt firmware

but this old, 50 euros hardware can't handle gigabit connections. I bought it when I was on ADSL 24Mbps and when i upgraded to VDSL, CPU was always at 100% when someone was downloading at max speed, plus that the memory was near its limit . So finally I had to ditch the archer and buy a quad core router (dl-wrx36) and find my peace.

edit : when I had problems like card negotiation at 100Mbps instead of gigabit it always LAN cable fault.

Thanks a lot for that... I will read it in details tonight.

when I had problems like card negotiation at 100Mbps instead of gigabit it always LAN cable fault.

Don't worry, I know about that! But no... The Alcatel Lucent ONT has a bug* that makes it fall-back to 100mbps on every occasion... Forcing it to negotiate at 1000mbps fixes the issue. I had the same problem at work with a full fledge Unifi Router and switch stack...

*Not sure if a bug or a "feature" by Bell Canada to ensure you use their hardware instead of your own

Further questions:
I might transform my 2 Archer C7 v5 in meshed Access point then... Wifi performance is great on those routers...
I was looking at RPI4 compute modules or full RPI4 to build a low power Wireguard VPN for the house (my network has redundant power everywhere and can be accesses through the Router's VPN for now)
Maybe I could fit it with a secondary network card to make it route the traffic...
Do you guys have a bit of experience with RPI4 devices? can they switch/route at gigabit speed both directions? (with more than one port of course)