RUTM50 Fails to Connect to Carrier

NETWORKING SOLUTIONS
1

Hello, I am using numerous RUTM50 devices and have been experiencing a connectivity problem on some of them. It appears that when connect to T-Mobile, sometimes the network assigns an IPv6 address and sometimes it assigns an IPv4 address. When an IPv6 address is assigned, the RUTM50 displays errors in the system log, and attempts to reset the connection and try again, getting stuck in a loop and eventually failing over to the other SIM card slot (which we have populated with an alternate carrier). It appears as though the device cannot use an IPv6 WAN address - note I have also seen issues with using WAN6 with wired connection and IPv6 and there are other community posts on this (for example, OpenVPN client disconnected every second hour - #8 by DanLun).

On systems that function, I am running older firmware: RUTM_R_00.07.11.1 with modem RG520NNADBR03A01M8G_01.001.01.001.

On systems that new function, I am running newer firmware, for example: RUTM_R_00.07.12.2 with modem RG520NNADBR03A01M8G_01.001.01.001.

The specific errors I am getting are:
Thu Feb 13 08:02:09 2025 daemon.info mobifd: [gsm.modem0] Attempting to establish connection to operator with “30s” of timeout
639 Thu Feb 13 08:02:09 2025 daemon.info mobifd: [gsm.modem0] Connected to operator “310260”
640 Thu Feb 13 08:02:09 2025 daemon.info mobifd: [gsm.modem0] -CFUN- Functionality: “Full”
641 Thu Feb 13 08:02:09 2025 daemon.info mobifd: [gsm.modem0] -COPS- Mode: “Auto”, operator: “310260”
642 Thu Feb 13 08:02:09 2025 daemon.info mobifd: [gsm.modem0] -CREG- Mode: “Enabled (with location information)”, status: “Not registered”, LAC: “”, cell ID: “”, technology: “Unknown”
643 Thu Feb 13 08:02:09 2025 daemon.info mobifd: [gsm.modem0] -CGREG- Mode: “Enabled (with location information)”, status: “Not registered”, LAC: “”, cell ID: “”, technology: “Unknown”
644 Thu Feb 13 08:02:09 2025 daemon.info mobifd: [gsm.modem0] -CEREG- Mode: “Enabled (with location information)”, status: “Not registered”, LAC: “”, cell ID: “”, technology: “Unknown”
645 Thu Feb 13 08:02:09 2025 daemon.info mobifd: [gsm.modem0] -C5GREG- Mode: “Enabled (with location information)”, status: “Registered, home”, LAC: “”, cell ID: “4480246071”, technology: “E-NR-5GCN”
646 Thu Feb 13 08:02:09 2025 daemon.info mobifd: [gsm.modem0] IP address on PDP context “1”: “38.7.251.144.121.9.192.232.10.211.223.81.105.71.228.236”
647 Thu Feb 13 08:02:09 2025 daemon.err mobifd: [gsm.modem0] Incorrect PDP type on PDP context “1”, reseting it
648 Thu Feb 13 08:02:10 2025 daemon.err mobifd: [gsm.modem0] GSM error in “mb_reset_pdp_context:208” (Invalid response)
649 Thu Feb 13 08:02:10 2025 daemon.err mobifd: [gsm.modem0] Failed to reset PDP context

The device then does this in a loop until it hits max retries and then switches SIMs.

As I am writing this I found a possible workaround. By setting the PDP type in the WWAN interface settings (with advanced view enabled) to IPv4/IPv6 the device is able to connect to T-Mobile, however it is not able to connect with a default setting of IPv4 PDP type. With the older firmware, the IPv4 PDP type works as expected. I verified with T-Mobile that their network does not yet support IPv6.

Based on the above information, it appears as though there is a bug in newer firmware related to PDP types.

2

I am having the same exact problem, where the connection to the carrier never finishes.

I recently ordered 12 RUTM50. Out of the 12, 3 so far have this problem. The issue affects all the carriers I have (AT&T, T-Mobile, Verizon). They don’t connect to 5G bands, 4G LTE, etc.

One the 3 that aren’t working, we thought that upgrading the firmware would be the solution. Did you also try rolling back the firmware?

I will try your suggested workaround.
Lastly, does anyone know how to create an RMA?

4

Hi @mtk_matrix ,

The error message

647 Thu Feb 13 08:02:09 2025 daemon.err mobifd: [gsm.modem0] Incorrect PDP type on PDP context “1”, reseting it

This indeed indicates that the PDP type (IPv4 / IPv6 / IPv4v6) was configured incorrectly. It’s worth noting, that starting from RutOS 07.06.x release, the default PDP context on our devices is IPv4v6 (dual stack), so either this setting was changed manually on your device, or the configuration was carried over from older firmware releases.
Additionally:

I verified with T-Mobile that their network does not yet support IPv6.

T-Mobile USA definitely does support IPv6 on their network, and if I recall correctly, they were one of the first US carriers to adopt it.

I’m not certain about why you’d sometimes receive IPv4, and sometimes IPv6, but perhaps you’re using AutoAPN feature? If so, it could be that the device choses different APNs and this results in your described behavior. Could you try disabling AutoAPN in Network → Mobile → General and choosing one of the APNs in the list? Refresh the connection a few times and check if the behavior repeats.

Best regards,