Very slow VPN speed on Flint2

Technical Support for Routers VPN, DNS, Leaks
1

Hi,

I have a great speed problem with Flint2 while using VPN.

Without VPN it works well.

Situation BEFORE Flint

  • Standard router of my service provider: ADB Crow Ax5400.

  • Speed test WITHOUT Wireguard made with Speedtest.net: about 100/20 Mbps

  • Speed test WITH Wireguard made from the same site: about 70/18 Mbps

Note: the Wireguard server is a VM on Proxmox on the same lan.

Situation AFTER Flint

  • Speed test WITHOUT Wireguard made from the same site: about 100/20 Mbps

  • Speed test WITH Wireguard made from same site: about 20/18 Mbps

The download speed dropped down dramatically.

Note: tested both internal Flint2 Wireguard server and my personal VM Wireguard server, same results.

The problem seems to be in Flint2.

2

I don’t supose you have a WG conf for a provider like Mullvad, IVPN, Surfshark, etc.? Something is defiantly off. My Flint v1 gets 115 Mbps down over WG, easily.

3

No VPN client activated on Flint, no commercial VPN provider.

4

Yeah, I just don’t know then. Even the cheapest I’ve seen, Surfshark, advertises 1 Gbps locations but if you don’t have one, you don’t have one. Do you have a spare machine that you can boot a live USB & set up a WG peer to hardline to the Flintv2 via its auto-generated confs? WG is technically all P2P so it shouldn’t technically matter if the Flintv2 is the ‘WG Server’ in a S2S as long as the routes are good. See below for a template:

You could also check by & even self host Open Speed Test.

5

Did you ever figure out the problem? I just got the Flint 2 and also have much slower speeds with VPN compared to my old Flint 1. 4mbps vs. 10mbps using openvpn.

6

Both values are pretty low, how much speed provides your ISP?

7

I have the same issue on my Flint2 GL-MT6000. The VPN speeds are around 200Mbp/s when using the client on the router. When using a client on my PC, the speeds are closer to 900Mbp/s using the same config.

This is using OpenVPN on the latest GL-MT6000 update.

Tested 2 Different VPN providers, UDP and TCP configs. Also tested 2 different ISP's and same results. Peak speeds are 220-230Mbp/s.

CPU and RAM usage are both sitting fairly low and the resources do not look to be over utilised.

8

After looking at the issue, I have a feeling, the router when it is used to initiate the VPN connection, does not use mss-fix packets. This then causes an MTU segmentation fault, which in turn causes the packets to be resent and cause the drop in speed.

9

[UPDATE - Issue is not the Router]

I tested on the Router interface using the NordVPN OpenVPN config file. The speed was tested at 200-230Mbp/s. I then disconnected this, and connected via the NordApp, and the speeds were as expected at 900Mbp/s.

I have completed more testing by using the OpenVPN GUI on my Windows PC without any other VPN connected, and this shows the same results as the Router with speeds of 230-300Mbp/s.

I have looked at the config and would suggest the mms-fix of 32bytes is the cause, however without being able to drop this to 1500, I cannot rule this out one way or the other.

The mss-fix looks to be applied for Radius, and is used on OpenVPN connections.

10

It‘s not an issue. The max OVPN speed on Flint 2 is around 190 Mbps as the device information website tell.

11

It's not the router, it looks to be the OpenVPN config. 190-200 looks to be due to the MTU size.

12

It is the router because GL officially tells that the max speed is 190 Mbps.

See Product Comparison - GL.iNet

13

and the OpenVPN config when used not on the router but with the OpenVPN GUI gives the same speeds. I also saw consistent speeds above 190, up to 230. if it was limited to 190, i would suggest we see a hard cap.

14

Might be but does not matter for the initial question: You won't be able to get much higher than 190 Mbps on the router itself.

15

Going by the link you posted, you're right. Question, why? OpenVPN say they have no cap.

16

Guess because OpenVPN does not support multi core usage and therfor capped by CPU.

I would recommend WireGuard anyway.

17

I'll need to get hold of the Wireguard config. Nord has a guide for OpenVPN, not so much for wireguard.

18

Because Nord sucks.

But we have some guides:

19

Tested Proton, full speeds across the board with the free version. Definitely an OpenVPN issue (Nord.)

20

Open Vpn max speed around 200mbps.
Wireguard max speed around 900mbps.
@admon is right.