Re: PSA for Netgear LB2120 using excess 4G Data


PSA for Netgear LB2120 using excess 4G Data

PSA: If you purchase a LB2120 and put the device into bridge mode you may see exsessive amounts of data be used. 


So these 4G modems, when in bridge mode have been reported using exssive amounts of 4G data.

For example:


Although the user above says that they had resolved this by putting it back into Router mode. If your like me and are using it as a WAN fallback you will bridge Bridge Mode.


Being quite frustrated as to why this device was burning through the amount of data it was 40GB at this stage, I looked into the traffic logs to find that the majority (98%) of traffic was going to google dns servers.


Looking through the device, I found out that it was pinging google dns servers to detect whether it was online or not! Really! Why can't the device just use the connection state of each connection and determine its state based from this? Anyway... 


So firstly, if you need to use this device in Bridge Mode and do not want to waste 40GB of 4G data in about a week, do the following: 


  • Go to Settings > Advanced > Failover
  • In the IPv4 Addresses box add a new IP address of Do the same for IPv6.
  • Now delete the other address. In my case it was google dns which is and the IPv6 which was These MUST be removed!
  • Verifiy that you have now only got in both IPv4 and IPv6.
  • Save this config. Problem fixed.


To explain why and what this does. The way this device has been setup by netgear, they use a ping method to detect the state of the connection being active or offline by reading a response back from google dns, and This is what is actually using the data. Each time this runs, in my case every 5 seconds generally uses about 5-10mb of data. As you can imagine this will use a lot of data quickly if left alone.


Now as it was reported in the link posted above, changing the device operation mode to Router would be okay, as its most likely going to be setup with a ADSL2+/NBN connection which may not be metered. But still know, if the above settings are still set to google dns, there would still be considerable amount of data being used just to detect the state of the connection. 


When in Bridge Mode this setting should be turned off/ disabled. Technically I would say that when you have this device in bridge mode this would be most likely connected to another device managing the failover to this device. In my case this is what I have setup. 


ROUTER > NTD (NBN Connection)

                > Netgear LB2021



Anyway the point of this post is just to hopefully help someone else who searches why there device is burning through a bunch of data and not get a huge 4G data bill like I did. 




@netgear  - I would be updating the firmware to fix this problem. When looking into this online, your device got quite a lot of negative reviews about the excess data consumtion. This would not be hard to implement into a firmware patch in the future. Even just changing the connection state detection to use another method.  


The negative reviews for your reference: 




Model: LB2120|4G LTE Modem
Message 1 of 4

Re: PSA for Netgear LB2120 using excess 4G Data

I read your post with interest, as I have had the issue of excessive data use with this model in 'Bridge Mode', but in my case, its not set in failover mode, i have fixed it to 'Bridge Mode' fulltime, as I only have a 4G internet service.... in my case, this excessive data use was only when used with Telstra 4G, not with Optus 4G.... I was using Optus 4G for a few years with no issues around unexpplained data use, but when I switched to Telstra 4G late last year, this isssue was apparant immediately, the config had not changed between carriers other than the APN.... so there is something happening with Telstra, but they would not support me as they say they don't support 'Bridge Mode'...for now, unitl I know the cause, I have had to bench the LB2120 and use anither device which was not ideal for my network setup.



Message 2 of 4

Re: PSA for Netgear LB2120 using excess 4G Data

Yeah, weird. Not too sure what physically changes with the software when you switch between providers, but I wonder if its programmed with some type of network reset while it applies the new profile from the provider? When you change from Optus to Telstra, you would be applying new APN settings, but its likely this would trigger the software to use a new profile during this transition. This profile might be setup with the default DNS settings that I changed above?    - Just thinking out-loud. Smiley Happy 


Did you try out the above steps to see if you have any success? I believe you can still set those settings I describe above in both Bridge and standalone modes. 


Since posting that initial write up my LB2120 has been going rock solid and have I been using it on and off reliably with my Ubiquiti Edge Router. Good speeds when I need it. Smiley Happy 


Anyway good luck with your! 


Message 3 of 4

Re: PSA for Netgear LB2120 using excess 4G Data

Thanks for the quick response, I’m also using a full Ubiquiti network with there Security gateway device, it works like a treat with the LB2120 in bridge mode, at least with Optus 4g , I’ve had to put it aside for now with Telstra, but I will get it out again and check the settings you mention 😀😀
Message 4 of 4
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