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I am using TRB-255 with firmwareTRB2_R_00.02.06.1. My simcard is limited to 50 MB per year / LTE-M. I want to achieve that there is no traffic except when "data to server" is sending measurements from modbus, few times a day

When I monitor "status"/"realtime data" / "Traffic" I notice small but continuous traffic such that I am already spending megabytes per day.

Looking at "Connections" there is a long list, with many lines a like:

IPV6 UDP [fd8b:f271:22f9::8574:412:ec0a:6174]:55127 [fd8b:f271:22f9::1]:53

When I change firewall "zones" "wan-reject" output: reject then no traffic is measured but also data to server is not working. Can I make an exception with firewall or custom rules to just allow data to server?

I have no experience in iptables unfortunately

Thanks in advance

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Thank you for contacting .

Regarding your query .

Could you make it more clearer ?

1)You want other users to use WAN when the data is not being sent to the server and when data to server starts stop other users ? Right or not ?

2)You want to disallow all the users for all the time and only allow data to server functionality for all the time? No user should use internet ? Right or Not

Please correct me .

IF you want to allow only one user you can and disallow all others , you can simply create a new forward rule .

Where you will create two rules :

1) To disallow all others

2)To allow only 1 IP address or mac address of the device that is sending data .


I hope it helps.



Hi Ahmed,

Thanks for the answer.

I use the TRB255 to just fetch MODBUS/RTU data and send this with https to a server (data to server). Lan port is not used besides configuration/test time.

I want to make sure that there is no mobile traffic besides the https posts.


Yes , as mentioned you can configure traffic rules to allow data to server only.


Also you can check in tcpdump what services are using the data . Then disable those services.

Thanks .