Slate GL-AR750S-Ext - Slow Wireguard Upload Performance


I have been getting poor performance with my Slate GL-AR750S (client) connected to my Flint GL-AX1800 (server) router at home. I sometimes get decent speeds (atleast 6mb upload), but often 0.6mb upload. My computer is connect via ethernet to my Slate. Its not consistent and I don’t know why.

On my iPhone connecting to my Flint server at home I get consistent 24mb upload. This is using the same WiFi connection.

Any help would be greatly appreciated!


On your AR750s, can you try setting the Wireguard MTU size to 1280? As I’m on the road almost full time now, and using my AR750s in many different places, I have gone to setting my MTU on my AR750s to 1280 as I’m never sure how the router I’m connecting my AR750s to is setup, and I have found having a too small MTU is much better then a too big one, as a MTU too large gives me very inconsistent results.

Using a 1280 MTU on my AR750s to my AR300s running as a Wireguard server that is located in another country, I’m seeing up to a 13 Mb upload, and up to a 30 Mb download using an internet provider that gives me 50 down, 15 up link at the place I’m currently staying at.

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Thanks Eric!

Previously I did not have any value entered for the MTU, but now using 1280 as you recommended I am getting 25 down and 16 up.

Should I adjust anything on my Flint GL-AX1800 server also? I would like to get the best speed if possible!

Thanks again!

I have not found any tuning changes that help on the server side. On the client side, you may get a little more speed by increasing the MTU size little by little, until you find the perfect fit, but if you change the location of your AR750s, you may have to re-find the perfect fit.

I prefer to just use a MTU of 1280 for Wireguard on my travel routers, as it is close to as fast as it will get, and just works. Since I move around a lot, just works is very important to me.


Thanks Eric for the explanation. Makes sense and really appreciate the explanation! I will the the server as is then.

If you know possibly, what is the difference between the higher and lower MTU values? Are there any advantages or disadvantages? Or is it just purely a technical thing?

The MTU is a technical thing.
Imagine I write a very looooooong line and you can’t read it, because your display is only 20 characters wide. Than you ask me to write shorter lines.

The Text above would be:

The MTU is a techni
Imagine I write a ve

But as sender I am able to define the line size

So if I know your
Setup, I am able
to limit the width
of my text.

So in this example the MTU is 20.
I could also write Texts with 5 characters, but then the whole sense would disappear. The biggest possible value will be the best. Plus the Overhead, I need to add things like line numbers, in case of the transmission will mix up.
The overhead defines what will be the best value. 1500 (LAN default) - Overhead.

An than there are Jumbo frames, too … But all this will be better with IPv6, because IPv6 will send a Package, this will be answered and before a data transmission will be established the communication partner will negotiate the best value. Works good, most times.

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Simplified, the MTU is the size in bytes of the data packets being sent. As each packet has an overhead, the bigger the MTU size, the less packets are needed for a given message, and the more efficient the data transfer. Between your AR750s and your Flint can be 10 or more routers, depending on where they are both located in the world. If any of these routers cannot pass your packet’s MTU size, the packet will have to be split and reassembled. This splitting and reassembly is a costly operation that you want to avoid.

The reason for using 1280 is that is the minimum size needed to support both IPv4 and IPv6 packets that are carried by Wireguard.


Thanks LupusE! Thorough explanation. Makes sense!

Thanks Eric! Makes sense why you chose 1280. Appreciate the followup explanation.