Public bug reported:
I have a reproducible WWAN recovery problem on Ubuntu 24.04 with an
Intel XMM7560 LTE modem using the IOSM/MBIM stack.
Expected behavior
After ModemManager is stopped and started, the modem should reconnect
and restore the WWAN data connection without requiring a full system
reboot.
Actual behavior
The modem successfully powers on, registers on LTE, reaches registration
state `home`, and reaches packet service state `attached`, but the MBIM
data bearer cannot be established. NetworkManager retries automatically,
but the bearer attempts repeatedly time out.
Reproduction
Initial state:
- ModemManager active
- NetworkManager active
- modem state `connected`
- access technology LTE
- registration `home`
- packet service `attached`
- WWAN is the active default route
Run:
sudo systemctl restart polkit.service
On this Ubuntu system, `ModemManager.service` has:
Requires=polkit.service
After=polkit.service
Restarting polkit therefore causes ModemManager to be stopped and
started.
After the restart, ModemManager comes back and the modem again reaches
LTE registration `home` and packet service `attached`, but it remains in
state `connecting` and the WWAN default route is not restored.
After the connection attempt reaches its timeout, the following messages
are reproducibly observed:
failed to connect modem: timeout
port wwan0mbim0 timed out 2 consecutive times
connection attempt #1 failed: Transaction timed out
couldn't connect bearer: Transaction timed out
NetworkManager retries, but subsequent bearer connection attempts time
out in the same way.
Recovery
A normal full system reboot restores WWAN immediately:
- modem state `connected`
- LTE registration `home`
- packet service `attached`
- WWAN default route restored
This recovery has been verified multiple times.
Original observation
The problem was originally discovered during normal Ubuntu package
maintenance. NetworkManager was restarted while its package was being
configured and WWAN successfully recovered.
Later in the same maintenance sequence, polkit was restarted, which
caused ModemManager to stop. After that ModemManager restart, the same
persistent MBIM bearer timeout occurred.
I then reproduced the problem independently of package maintenance using
only:
systemctl restart polkit.service
Therefore, a package upgrade itself is not required to trigger the
issue.
Environment
- Ubuntu 24.04
- amd64
- kernel 6.8.0-137-generic
- ModemManager 1.23.4-0ubuntu2
- NetworkManager 1.46.0-1ubuntu2.8
- polkitd 124-2ubuntu1.24.04.3
- Intel XMM7560 modem
- IOSM / MBIM
- LTE
Important distinction
The modem does not fail LTE registration.
After the failure it still reaches:
- registration `home`
- packet service `attached`
The failure occurs when establishing the MBIM data bearer after
ModemManager has been restarted.
I would appreciate guidance on:
1. Whether this is a known Intel XMM7560 / IOSM / MBIM recovery problem.
2. Whether this modem should normally recover from a ModemManager daemon
restart without requiring a system reboot.
3. Whether there is a supported modem reset or reinitialization sequence that
should be attempted when MBIM bearer creation repeatedly times out.
4. Whether the problem is more likely to belong to ModemManager/libmbim, the
Linux IOSM driver, or modem firmware.
5. What additional debug logging would be most useful during a controlled
reproduction.
The report has intentionally been anonymized. Hostnames, IP addresses,
wireless network names, account information, SIM identifiers, IMEI and
modem serial identifiers have not been included.
ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: modemmanager 1.23.4-0ubuntu2
ProcVersionSignature: Ubuntu 6.8.0-137.137-generic 6.8.12
Uname: Linux 6.8.0-137-generic x86_64
ApportVersion: 2.28.3-0ubuntu0.1
Architecture: amd64
CasperMD5CheckResult: pass
CloudArchitecture: x86_64
CloudID: none
CloudName: none
CloudPlatform: none
CloudSubPlatform: config
CurrentDesktop: ubuntu:GNOME
Date: Fri Aug 14 10:03:55 2026
InstallationDate: Installed on 2026-06-18 (57 days ago)
InstallationMedia: Ubuntu-Server 22.04.5 LTS "Jammy Jellyfish" - Release amd64
(20240911.4)
SourcePackage: modemmanager
UpgradeStatus: Upgraded to noble on 2026-06-27 (47 days ago)
modified.conffile..etc.dbus-1.system.d.org.freedesktop.ModemManager1.conf:
[deleted]
** Affects: modemmanager (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug noble
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https://bugs.launchpad.net/bugs/2163470
Title:
Intel XMM7560 WWAN fails to reconnect after ModemManager restart on
Ubuntu 24.04
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