Vpn speed issue

Routers
1

Hello,

I use GL.iNet products for VPN use.

I use a Flint v1 in France as an WireGuard client, and a Flint 3 in the UK as a WireGuard server, always updating the firmware.

I have a mobile home in the south of France, which I use to access the Internet via 5G mobile data (SFR & FREE.fr), which is great here in France.

However I now have moved over to StarLink, currently setting it up prior to moving over to "Bypass Mode", which negates the StarLink router, and "hands" everything over to the Flint 1 router.

The problem is that if I link to the Starlink modem direct, I get 100+ Mbps, and if I link to the Flint I get 10Mbps or less. I got much better using the 5G setup.

Please can anyone advise - I've googled "everything", but not succeeded - any ideas, anyone?

TIA
Barry

Ultra Slow VPN & Timeouts
2

Hi,

Do you mean the following:

  • When client devices connect directly to Starlink without a VPN, the speed can reach 100+ Mbps
  • When the Flint is connected to Starlink, and clients connect to the Flint with the VPN enabled (routing traffic to your home exit in the UK), the speed drops to around 10 Mbps
  • When the Flint connects via a 5G network, and clients connect to the Flint with the VPN enabled (routing traffic to your home exit in the UK), the speed is higher than 10 Mbps

Is our understanding correct?

If so, the likely cause is poor network quality between Starlink and your ISP in the UK. In this case, there isn’t much that can be done aside from contacting or switching your ISP.

You could also try using OpenVPN in TCP mode to see if it improves performance. Since WireGuard uses UDP, it may be more susceptible to QoS when traffic crosses different networks or carriers.

4

Hello,

Thank you for your quick reply.
My reply to your questions are in BOLD,

  • When client devices connect directly to Starlink without a VPN, the speed can reach 100+ Mbps

    YES

  • When the Flint is connected to Starlink, and clients connect to the Flint with the VPN enabled (routing traffic to your home exit in the UK), the speed drops to around 10 Mbps

    YES

  • When the Flint connects via a 5G network, and clients connect to the Flint with the VPN enabled (routing traffic to your home exit in the UK), the speed is higher than 10 Mbps

    NO, 10Mbps or less

    Thanks,
    Barry

5

Could you please help test/provide the following:

  1. When the VPN is disabled, what speeds can the Flint achieve when connected to Starlink?
  2. What are your home broadband download and upload speeds in the UK?
  3. As we previously suggested, have you tested OpenVPN in TCP mode? If so, is there any change in speed?
  4. Do you have access to any commercial VPN services? If so, try connecting to a server near France—what speeds are you able to achieve?
1 Like
6

Could you please help test/provide the following:

When the VPN is disabled, what speeds can the Flint achieve when connected to Starlink?2.4Ghz = +-16Mbps, 5Ghz = +-38Mbps

What are your home broadband download and upload speeds in the UK?
Download: 64 - 72Mb
Upload: 16 - 18Mb

As we previously suggested, have you tested OpenVPN in TCP mode? If so, is there any change in speed?
You could also try using OpenVPN in TCP mode to see if it improves performance. Since WireGuard uses UDP, it may be more susceptible to QoS when traffic crosses different networks or carriers.

I am in France at the moment and don't have access to my Flint 3 server, so cannot set up OpenVPN, also I really like & prefer WireGuard’s speed and simplicity…

Do you have access to any commercial VPN services? If so, try connecting to a server near France—what speeds are you able to achieve?

130-150Mbps

Hope this helps.
Thanks,
Barry

7

In this case, the behavior seems expected.

Your home broadband upload speed in the UK is only around 16–18 Mbps. Considering the overhead of the WireGuard protocol, along with transoceanic/ISP-related losses, achieving around 10 Mbps download speed on the WireGuard client side is reasonable.

Were these results obtained by running a commercial VPN on the Flint and performing a speed test?

If so, we can see that when switching the VPN server to a location closer to France, the Flint is able to achieve expected speeds without issue. This suggests that the limitation is not due to the Flint’s performance.

8

So, a decrease in speed of 1/10 of non-VPN (+- 100Mbps without Flint 1, less than 10Mbps with) is to be expected?

and...

What is your opinion of the regular (every +- 1 hour for about 5minutes) time-outs?

9

As we discussed, your home ISP in the UK provides an upload speed of 16–18 Mbps. When using your home router as a WireGuard server, this upload capacity becomes the maximum theoretical download speed for your remote client.

After accounting for the 5–10% protocol overhead required for encryption, your maximum usable download speed is roughly 14.5–16 Mbps.

Achieving a 10 Mbps over a residential connection and long distances is actually a very good result. Unfortunately, we cannot exceed the physical speed limit of your UK ISP line.

Regarding the Timeout Issue:

To help us investigate, please clarify:

  1. Does the connection drop completely, or does the speed just stall?
  2. Do you have to manually reconnect, or does it recover on its own?
  3. Could you please provide some screenshots so that we can better understand the issue?
10

The bottleneck is likely WireGuard encryption overhead on the Flint 1 routing all Starlink traffic through your UK WireGuard server will cap speeds significantly depending on server upload capacity and distance. Try temporarily disabling VPN on the Flint 1 and testing raw Starlink speeds through it. If speeds recover, your UK server's bandwidth or the WireGuard tunnel is the limiting factor, not the Flint 1 itself. Also check if MTU mismatch is an issue try setting WireGuard MTU to 1412 for Starlink compatibility.

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