GL-AR150 4G USB modem tethering is slower than direct connection

I have a Huawei E3372H-510 modem on the T-Mobile network using a tablet/hotspot plan. When I plug the USB modem into my windows 10 PC directly and run I get 22-25 mbps and sometimes I can get 30mbps. Now if I connect the modem to the router, run the same (meaning same server as before) I only get 10 mbps-15mbps. Does the usb port on the AR150 router maybe not have full power for higher speeds? Maybe there is some software running on the router that is slowing down the traffic? This doesnt make sense. Btw both the router and the windows 10 pc have there TTL set to 65 so its not a network throttle issue. Some how the router is about 5-10 mbps slower then direct connection.

Is the router doing NAT/Firewall compared to the direct connection? If so I can see the CPU being a bottle neck, especially if it’s performing any kind of actual routing. The AR150 has a pretty weak 400Mhz CPU so it’s entirely possible that it just can’t keep up and you’re expecting too much from it.

For a test, trying removing the USB modem and connecting your AR150 directly to a wired WAN connection that you know is at least as fast as the 25-30mbps your testing. See if running through the wired WAN gets you the same speed drop, I would not be surprised if it does.

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the router has the preinstalled GL.inet firmware installed, so it does have some basic firewall stuff. I’ll install a fresh openwrt firmware without the gl.inet stuff and start from there. The modem is a usb modem (Huawei e3372h-510) so I can only test it directly plugged in to my windows 10 tablet. The tablet get almost double the speeds the router sends out so there is definitely something going on. I wonder if it could be driver related? Ill get back to you tonight with my findings.

Could also be the mode that you’re running it in on the AR150. Have you enabled QMI or MBIM instead of just the default 3g mode? Not sure what protocol that card supports but higher speeds definitely require something more advanced than the standard serial connection.

@jolouis im new to this, what is QMI or MBIM? I’ve done some quick searches but I cannot find much about my USB Modem specifically. There is another similar, the Huawei E3372H-153, and from what Ive read it does support QMI. Not sure if that means mine will support it. I have read something about putting the modem into ‘stick’ mode instead of ‘hilink’ mode and using R00ter.

judging by this article here the GL.inet firmware must be doing something interesting. Im going to install a fresh copy and follow the steps.

The firmware currently installed on the router is here:

Ah ok that particular modem runs by default in Hilink mode, which means it’s basically doing all the routing/etc on the modem itself (think of it more as a “modem/router”). So when you connect it, it should just be showing up as an extra network interface. Dont worry about the QMI/MBIM stuff not applicable here as the network interface should be more than capable of handling the bandwidth.

My suspicion then goes back to the original point of CPU power on the AR150. You can reduce the CPU needed by turning off NAT, but that pretty much defeats the point of using the router unless your only intention is to be able to share the connection with more than one device at a time?

well because the modem and the router both have NATs, any device connected to the router gets ‘double NAT’d’. This causes things like PLEX not to work. Im basically running my home network off of tmobile, which is cost effective but for whatever reason my speeds are slow using the router. Maybe I just need a beefier router like the AR300 or GL.iNET GL-MT300N-V2. Ill start with slimming down the firmware, the installed app list is huge in the router.

Wow never thought I’d hear somebody say North American Cell provider is cost effective in any definition of the term ;o)

As long as all of your devices are behind the same layer of NAT I don’t see why it would cause you problems. The only time it becomes an issue is when you have some local stuff on one side of the first NAT, and some local stuff on the network wedged between the two. The bigger issue is usually related to port forwarding/etc, but if youre on a cell network that all goes out the window anyway as most of them don’t let you have any kind of inbound connections anyway (they’re in essence running big NATs between their network and the real internet).

Anyway you probably just need a beefier router. One thing you could try is SSH into your AR150 and run the “top” command. That will show you real-time CPU usage. With that open, start a large transfer or speed test. If you see anything peaking out at 100% CPU then you know for sure that’s the limiting factor.

Awesome I really appreciate your help! And yeah cant beat 30mbps unlimited data for $29.99 a month. Now just to get that speed to all my devices is the trick.

That modem has an IP conflict with the router, so the first thing to do is change the router LAN IP to something other than

Yeah I already had that done. other wise I would get no internet

After reading through the thread - that would be the first change made…

Logging into the GL-iNet WebGUI - on the left side - @GettinFishy - do you see the WAN side as Tethered or 3G/4G Modem?

With HiLink - it’s USB ethernet - should be a “Cable” interface - so might have to go under the hood in advanced settings and create a new WAN interface there.

Also a choice should be made - who does the routing? The Huawei device or the AR150M? Not sure if you can bridge the Huawei device.

Huawei modems can be a pain - between USB Mass Storage, mode-swap into QMI, etc… sometimes they try to be too helpful, and mostly focused on Windows.

AR150 should have more than enough horsepower to push wired speed, even with NAT at 30Mbps

If the modem is not hi-link, then generally using PC and Huawei software will be faster. I suspect that they have some AT commands to optimize the network. Also Huawei uses NCM protocol which the router may just use ttyUSB connection.

In ttyUSB modem the router can achieve more than 20Mbps without problem. But there may be some other factors affecting the speed.

All, I was doing some testing last night and I couldn’t get a consistent speed with my tablet. In order to properly test the router I first have to get a constant speed with using my tablet and the usb modem. I tried several tests using the same server and kept getting different results. Something is strange with the way the modem connects to the t-mobile network. I would run a test, get 10mbps. Change my APN settings from ‘’ to ‘’ and then back to ‘’ and my speed would go to 25-30mbps. Then a few minutes later I would run the test and my speed would be back down to 10mbps. It seems very sporadic. More research has to be done on the USB modem before ill continue playing with the router.

where did you end up on this?