RUT240/241 (probably others) dropping connections/packets during low utilization

Networking Solutions
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I encountered an issue back in ‘23 with a RUT240 where, under low/minimal utilization, the device would randomly drop up to 50% of inbound and outbound packets. Recently I’ve encountered the same issue on a RUT241 running the latest firmware. I’ve been actively troubleshooting directly with Teltonika tech support up until a couple weeks ago where the issue appears to have lost traction with them (escalated to development and haven’t received any updates). Would like to get feedback from other users on how widespread this issue is (or isn’t).

The dropping of outbound traffic can be observed by having a device connected to the RUT’s LAN that generates very little and/or infrequent internet traffic, such as a firewall that’s using the RUT as a backup/failover connection and only occasionally (every 1-5 seconds) sending an outbound ping to check whether the connection is up. Up to 50% of the outbound packets were being dropped in this scenario, leading the firewall to believe that the internet connection was down or flapping. I can see remote monitoring and control applications using RUT having a similar issue, where the RUT is connected to an industrial and/or IoT device that makes few/infrequent outbound connections.

The dropping of inbound traffic is observed by having the RUT setup with cellular service that provides a static public IP, and pinging that public IP from an external host. With one or more clients/devices connected behind the RUT (on it’s LAN) and making various internet connections you’ll observe expected latency and little to no drops from the inbound pings. However, if you don’t have any clients/devices connected to the RUT (nothing on the LAN that’s generating internet traffic), or a device that generates very little/infrequent internet traffic (eg. firewall using the RUT as backup/failover connection) you’ll notice significant increase in latency, to the point of packets being dropped (up to 50% depending on the frequency of the pings).

It’s like, if there’s minimal connections/utilization, the RUT (or just it’s cellular interface) goes to “sleep”. Anyone else seen similar? Thanks.

4

Hello,

Our R&D developers are still actively investigating, testing, and working to reproduce or understand the packet-dropping behavior you’ve reported with RUT240/241 devices under low-traffic scenarios. Once we receive any concrete feedback or findings from the developers working on this issue, we will update you directly and privately.

In the meantime, if there are other users who have experienced/are experiencing similar inbound or outbound packet loss on RUT240/241 devices, your feedback and observations would be greatly appreciated to address this behavior more effectively.

Best regards,

1 Like
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Hi, I’m having very similar problems. I’ve tried everything, but I don’t know what else to do. I have other RUT models, but this is the only one that’s giving me problems. It disconnects from mobile data every 2 hours or so, even though I’m connected to it remotely via RMS. I have to reactivate it by sending an SMS with “passrouter mobileon”; that’s the only way I can manage it. I send 5-6 SMS a day, which is out of the question.
I absolutely must fix this problem. HELP ME!
RUT241
RUT2M_R_00.07.17.1
(Gianluca from Rome, Italy)

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Thank you for your reply. However I think you’re having a different issue as I’m not seeing the cellular connection “disconnect” - at least the device/logs don’t show this. And I’m not experiencing sustained outages, just very frequent periods of high latency and packet loss whenever the RUT is under low/minimal utilization.

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It occurred to me that I should check/test the RUT’s ethernet WAN interface (eth0.2?) to see if this issue affects that connection/interface as well, and it does not. This issue appears to only affect the RUT’s cellular connection/interface.

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