LTE reset on LMT 5G

RouterOS General
1

I'm getting intermittent disconnects on lte

lte1 mbim: modem's control interface have reset (3)

lte1 link down

lte1 mbim: >>> E #18 - conn_ext: network params, error: NO_DEVICE_SUPPORT

happens intermittently - up to several times a day. Recovers by itself within a minute

LMT 5G 7.20 (stable)

Build Time 2025-09-29 09:33:57

Factory Software 7.1.1

2

@dimkin did you find a solution to this? I'm having the same error with a ATL & rm520n-gl, I think a firmware update of the card might help

3

no solution found/advised by MT.

went to claude.ai ( haha, so hype ) and it said to me this is know bug

This is a known issue with MikroTik's MBIM (Mobile Broadband Interface Model) driver losing its session with the modem. Here's what's happening and how to fix it:
What's causing it
The modem firmware loses sync with the MBIM control interface — often triggered by weak signal fluctuations, thermal issues, or the modem silently trying to switch bands. The NO_DEVICE_SUPPORT error usually means the modem stopped responding to the driver mid-session.

none of those helped

Fixes to try (in order of effectiveness)

  1. Set a fixed LTE band
    Forcing a stable band stops the modem from hunting for 5G or switching bands mid-session:
    /interface lte set lte1 band="1,3,7,20"
    Adjust band numbers to what your carrier actually uses. This alone fixes the issue for many people.
  2. Add a watchdog script to auto-recover faster
    Instead of waiting for the router to self-recover, a script can detect the drop and restart the interface:
    /system scheduler add name="lte-watchdog" interval=2m on-event={
    if ([/interface lte get lte1 running] = false) do={
    /interface lte disable lte1
    :delay 5s
    /interface lte enable lte1
    }
    }
  3. Disable 5G/NR entirely in the modem
    If the modem keeps probing for NR (5G New Radio) in the background, it can destabilize the LTE session:
    /interface lte set lte1 nr-disable=yes
    Not all RouterOS versions expose this — check if it's available with ? tab completion.
  4. Lock the network mode explicitly
    /interface lte set lte1 network-mode=lte
    This prevents the modem from ever attempting 5G fallback negotiation.
  5. Tune the MBIM session keepalive
    Some users fix this by lowering the MTU slightly (helps with fragmentation issues that can kill the session):
    /interface lte set lte1 mtu=1400
  6. Update RouterOS and modem firmware
    MBIM reset bugs are frequently fixed in point releases. Check:
    /system package update check-for-updates
    And in Winbox: WebFig → System → RouterBOARD → Upgrade to update the modem firmware separately from RouterOS.

Recommended combination
For most people, steps 1 + 4 + the watchdog script resolves this completely. Start there before trying the others.
If the resets still happen after all of the above, it's worth checking the modem temperature — sustained resets can also be a thermal issue, especially in outdoor or enclosed enclosures.

4

Of course not. AI is not trained to tell you "I don't know". So it makes up stupid exercises for you.

5

sadly, stupid AI was trained on data, where people complained about MBIM error, w/o resolution in related forums.