RUTX50 mobile data drops every few minutes and reconnects automatically

Networking Solutions Issue
1

Hello,

I am experiencing a recurring connectivity issue with a Teltonika RUTX50.

Device Information

  • Device: RUTX50

  • Firmware: RUTX_R_00.07.23.6

  • Modem: RG501Q-EU

  • Network Operator: SMARTY (Three UK)

  • APN: three.co.uk

  • Connection Type: 5G (NSA), VoLTE

  • PDP Type: IPv4

  • WAN Mode: NAT

Issue Description

The router starts normally and internet access works correctly after boot.

However, after a few minutes, the internet connection drops for several seconds before automatically reconnecting. This behaviour repeats continuously throughout operation.

The outage is brief, but it is enough to interrupt active sessions, video calls, and other internet-dependent services.

Troubleshooting Already Performed

  • Tested multiple SIM cards

  • Tested in multiple geographic locations

  • Tested with an external outdoor antenna

  • Factory reset and reconfigured the router

  • Verified APN settings

  • Confirmed issue occurs regardless of location or SIM card

The behaviour remains identical across all tests.

Current Mobile Signal Information

  • Connected Band: LTE B28

  • Bandwidth: 10 MHz

  • Signal Quality: 26% (Fair)

  • RSSI: -71 dBm

  • RSRP: -103 dBm

  • RSRQ: -13 dB

  • SINR: 10 dB

Current Mobile Settings

  • VoLTE: Auto

  • Preferred Network Type: 5G/4G/3G Auto

  • 5G Mode: Auto

  • Band Selection: Auto

  • Low Signal Reconnect: Disabled

Log Findings

From the Troubleshoot package, I can see entries similar to:

Network device 'qmimux0' link is down
Interface 'mob1s1a1' is now down
Mobile data disconnected (internal modem)

followed a few seconds later by:

Network device 'wwan0' link is up
Interface 'mob1s1a1' is now up
Mobile data connected

This suggests that the mobile interface itself is dropping and reconnecting.

Additional Information

I have already contacted Teltonika support by phone and was advised to post here for further investigation.

I am currently generating a fresh Troubleshoot package after a clean reboot and without making any configuration changes, so that the issue can be captured under normal operation. I can provide this package and any additional logs requested.

Has anyone experienced similar behaviour, or are there any known issues with firmware version RUTX_R_00.07.23.6 that could cause periodic mobile interface resets?

Thank you.

2

Out of curiosity what do the event logs look like?

3

Thanks. I checked the event logs from the troubleshoot file and the main repeated entries are:

10:15:23 IPv4 connectivity started to fail
10:15:44 DNS resolution started to fail
10:18:34 DNS resolution restored
10:19:34 IPv4 connectivity restored

10:23:15 IPv4 connectivity started to fail
10:24:39 DNS resolution started to fail
10:27:11 IPv4 connectivity restored
10:27:20 DNS resolution restored

10:28:28 IPv4 connectivity started to fail
10:28:49 DNS resolution started to fail
10:29:49 IPv4 connectivity restored
10:29:52 DNS resolution restored

There are also many entries like:

dnsmasq: Maximum number of concurrent DNS queries reached (max: 150)

During the issue, local LAN devices still seem to work. Phones/cameras remain reachable and ping to the router continues working, but internet access becomes unstable and speed tests often fail.

So it looks like the LAN side is staying up, but IPv4/DNS/internet connectivity is intermittently failing.

4

Under Network, go to Internet Status and disable the feature. it is responsible for those logs. I have run into issues where it does cause cellular issues in the past and have started disabling it at every deployment. Hopefully it can help yours stabilize a bit.

6

Thanks for your support, I appreciate it.

I disabled Internet Status and tested again, but unfortunately the issue is still there.

One thing I’ve noticed is that the RUTX50 works fine on its own. The problems only seem to start once I connect it to our office network via a Cisco Catalyst 3560 PoE-24 switch.

The previous Three UK router worked fine on the same switch and cabling.

The router remains accessible and local devices continue working, but internet performance becomes unstable and Speedtest often stalls or fails.