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4G LTE Modem LB1120 extremely slow speed on T-Mobile

I recently picked up a Netgear 4G LTE Modem model LB1120 to use with my T-Mobile unlimited plan and when I plug the sim card in (from the phone that I'm not going to use anymore) I get extremely slow speeds when using the internet speed test, literally 0.5 mbps. This is extremely slow considering when I run the same test from the phone itself and get like at least 22 mbps. And if I tether the phone to a PC I get the same fast speed (I am using custom firmware on the phone). I called Netgear and they said they have to elevate the issue, but I haven't heard anything from them. After doing some research I'm starting to think that T-Mobile is recognizing the device as a hotspot and is throttling the connection, making the device basically a waste of money. It says it's connected at 4G speed on fast.t-mobile.com but I'm not seeing that kind of speed. Does anyone know how to get the fast speeds?

Message 1 of 14
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NETGEAR Moderator

Re: 4G LTE Modem LB1120 extremely slow speed on T-Mobile

Did you check with T mobile if for some reason the sim card will not work in that device?

 

DarrenM

Message 2 of 14
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Initiate

Re: 4G LTE Modem LB1120 extremely slow speed on T-Mobile

I had a similar experience. Found out that the new tmobile plans (T-mobile ONE) while they sounded great to get the unlimited 4G came with a catch that I missed: tethering (while unlimited) was at 3G speeds unless you got their One Plus or One Plus Unlimited add-on. And I found out in much the same way you did. So if you have that plan, that's probably what's going on. I'm interested to hear that while using custom firmware on your phone and tethering you didn't have the speed problem.

 

So the solution was to take that spare line i was going to use, kill it as a phone line, and add one back as a data plan (called TMO One Tablet) on my bill ($25) + add their unlimited hotspot to it (called ONE Plus International) (+$25)...now the device tethers at 4G unlimited for $50/mo. I switch the sim in between my LB1120 and their hotspot device depending on what i need it for that day. Works fine so far.

 

in summary-LB1120 works fine on TMobile as long as you have the right plan.

Message 3 of 14
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Tutor

Re: 4G LTE Modem LB1120 extremely slow speed on T-Mobile

I have exactly the same issue. Evidently T-mobile can tell when Data transactions are being requested by a ‘non-phone’ piece of hardware and will apply a speed limit of 0.5 mbps. NOTE: if you have the ‘One +’ plan enhancement, it will go faster until you hit 10gb of data consumption then it really slows down (can be way down to 0.1 mbps !)until next billing cycle. Does anyone know how to set up the Netgear LB1120 or LB2120 modem so it looks like a cell phone requesting data??
Message 4 of 14
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Guide

Re: 4G LTE Modem LB1120 extremely slow speed on T-Mobile

I found that you can change the ttl to do this.

 

you can do this with open source router firmware but in my case I can only do it on my pcs because I have an incompatible router

 

on your pc open a command prompt with administrator rights

type:

netsh int ipv4 set glob defaultcurhoplimit=65 (or 66 if you have a router or switch connected to the modem between your pc)

This will make the modem see your computer as if it was an android or iphone but I would suggest you don't go download crazy

 

I have the One+ plan and still had to activate HD streaming even though it said I didn't, it just gives you a pass for a few thousand days or something, lol

Message 5 of 14
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Tutor

Re: 4G LTE Modem LB1120 extremely slow speed on T-Mobile

Thanks very much. This appears to have worked for the PC. I shut down the PC and cold restarted. The internet speed test still shows a high download value (approx 16 Mbps).
Now - my cellphone connected to the same network as the PC only shows about 0.5 Mbps. Does the PC command string only provide a fix for the PC and not other devices connected to network?
Message 6 of 14
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Guide

Re: 4G LTE Modem LB1120 extremely slow speed on T-Mobile

The command I provided only changes the registry of your windows based PC. Your phone should already look like a phone on the T-Mobile network, but if you are connecting your phone to say your wifi router then the speed might be affected by that device, perhaps it's old or broken (I've had one die on me before). I would suggest not using the wifi and only using the data connection from T-Mobile.

Message 7 of 14
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Re: 4G LTE Modem LB1120 extremely slow speed on T-Mobile

I forgot to respond to this but basically my issue was T-Mobile screwed up when they activated the line and didn't give me my full server. I'm now under the impression that the custom firmware just resets all the tethering traffic's ttl to look like it's coming from the phone.

Message 8 of 14
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Tutor

Re: 4G LTE Modem LB1120 extremely slow speed on T-Mobile

Thanks for response. To refresh, my hardware configuration is:
Netgear LB2120 cellular modem (with T-Mobile cellphone SIM installed )with LAN port connected to Linksys EA6350 router.
The PC fix you provided works great. I wonder if there is a clever way to change the router or modem such that any device I connect to the WiFi network will not be throttled back by T-Mobile? That would be the big win !
Message 9 of 14
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Guide

Re: 4G LTE Modem LB1120 extremely slow speed on T-Mobile

You can using dd-wrt

Just google it

You'll need a compatible router and you'll have to do some research into how to set all traffic to the ttl in the setting

I haven't done it yet and I don't know when I will because I would have to get a new router so good luck if you attempt it yourself

Message 10 of 14
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Tutor

Re: 4G LTE Modem LB1120 extremely slow speed on T-Mobile

Looked at DD-WRT. Unfortunately the EA6350 doesn’t lend itself well to being reprogrammed. I may look at buying a WRT router a little later and jump into the water. I used to write code for ARM9 processors in my younger years. Used JTAG and full-up IAR development suite. Sounds like many use a serial connection to do bootstrap loading etc. Sounds like fun as soon as I get the time...
Message 11 of 14
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Aspirant

Re: 4G LTE Modem LB1120 extremely slow speed on T-Mobile

I just have the same question! I followed the step to fix my PC, but any other devices connected to the same network are still under 0.5mkp. Super slow. I have LB1121 model and I conncet this modem to an old router. Please let me know if there is any resulutions for using my actual unlimited 4g lte data plan on this modem, otherwise, there is no difference to use a mobile phone. Thank you~

Message 12 of 14
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Aspirant

Re: 4G LTE Modem LB1120 extremely slow speed on T-Mobile

Any way to do this fix on Mac?
Please advise.
Message 13 of 14
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Aspirant

Re: 4G LTE Modem LB1120 extremely slow speed on T-Mobile

If not T-Mobile then who else?

Can anyone recommend another LTE service provider that works with the Netgear LB1120?

And one that never throttles a data-only device?

I've been having great difficulty activating T-Mobile accounts for this type of gear.

Sure would like to try another service provider.

 

Message 14 of 14