Slow Internet Speed if Wireguard VPN is enabled

[aherped]

Router Model Affected
Models: RT-AX92U

Firmware Version Affected
388.1_0-gnuton1

Is this bug present in upstream Merlin releases too?
Don't really know, I think yes.

Describe the bug
When I activate Wireguard VPN, even if no client is connected, my internet speed inside my network drops from 940mbps to 450mbps with speedtest. If I disable Wireguard VPN I get 940mbps again with no problem.

I read about an optimization of Wireguard in newer versions of firmware but on other models.

https://www.snbforums.com/threads/why-does-wireguard-slow-down-the-entire-wan-lan-speed.81636/page-2#post-811997

It seems not to be a HW problem or limitation as they said that: "Thanks for all replies! With the new official 3.0.0.4.388.22068 firmware the problem seems gone! I get full 1 Gbps from clients outside the VPN and 400-500 Mbps from clients inside. So in the end it didn't seem hardware related."

Thank you

[lhayati]

I was about to post a throttle bug on my XT8 (RT-AX95Q). My speed upgrading to 388.1_0-gnuton1 dropped from 940mbps to about 300mbps. I read your post, turned off the wireguard server and immediately it bumped back up to 940mbps! Temporary solution I'll setup a wireguard server on a raspberry pi behind the router.

[starstar8]

after upgrade to 388.1_0-gnuton1, I got same issue on my Ausus Router TUF-AX3000, speed dropped to about 300mbps if wireguard server is running, when wireguard server turned off, the speed resume back to normal 900mbps.

[gesa]

This is because NAT acceleration gets disabled when Wireguard is in use. Something about a proprietary broadcom implementation of flow cache not being compatible with wireguard. You can confirm by checking out Tools > Network > HW acceleration. Speeds are limited to approx 350mbps without hw acceleration.

The good news is that 388.2 will use a new feature implemented by Broadcom/Asus which will allow non-WG traffic to still benefit from NAT acceleration, the bad news is it’s unclear when that’s released.

[mdburkey]

Looks like 388.2 Merlin mainline is out...hoping for a gnuton fork update for the XT8!