RosiKyu opened a new issue, #14520: URL: https://github.com/apache/cloudstack/issues/14520
### problem If a KVM host agent stops responding while its VMs keep running, the host is declared Down and its VMs are marked Stopped. At that point nics.broadcast_uri of their guest NICs is NULL. When the agent comes back, the VMs are set to Running again (event "Out of band VM power on"), but nics.broadcast_uri stays NULL while the network still has its VLAN (networks.broadcast_uri vlan://<vlan>). The VMs keep working on their current host. A live migration of such a router or VM to another host is refused. The destination does not create the per-VLAN bridge, and libvirt fails with: `Exception during migrate: org.libvirt.LibvirtException: Cannot get interface MTU on 'breth1-<vlan>': No such device` Management server log, for the router and the VM: ``` 2026-10-28 16:01:36,967 ERROR [c.c.v.ClusteredVirtualMachineManagerImpl] (Work-Job-Executor-28:[ctx-8e0f9702, job-152/job-153, ctx-152e1c05]) (logid:26e1c1f1) Migration command failed for VM r-18-VM on source host id=2 to destination host 1: Exception during migrate: org.libvirt.LibvirtException: Cannot get interface MTU on 'breth1-1658': No such device 2026-10-28 16:01:38,925 ERROR [c.c.v.ClusteredVirtualMachineManagerImpl] (Work-Job-Executor-29:[ctx-33afcd90, job-154/job-155, ctx-f4ba8d18]) (logid:3191a0e1) Migration command failed for VM i-2-17-VM on source host id=2 to destination host 1: Exception during migrate: org.libvirt.LibvirtException: Cannot get interface MTU on 'breth1-1658': No such device ``` The VMs stay on the source host and keep their network. A router reboot or a VM stop/start fills broadcast_uri again, and migration then works. Until then, the VMs cannot be moved off the host, for example for host maintenance. ### versions - **CloudStack:** 4.22.1.1 (management server and KVM agents). - **Hypervisor:** KVM on Oracle Linux 9, libvirt 9.0.0, two hosts in one cluster. - **Network:** advanced zone, Linux bridge (per-VLAN bridges breth1-<vlan>), isolated network with a VLAN, virtual router. The router service offering has **HA disabled** and the VM is not HA-enabled, so nothing is restarted while the host is Down. - **Storage:** NFS primary storage. ### The steps to reproduce the bug 1. Two KVM hosts (host 1, host 2) in one cluster. Isolated network N with a VLAN. Its router (service offering without HA) and a VM P with one NIC on N run on host 2, VM HA not enabled. Control: migrate the router and VM P to host 1 and back. Both work. 2. On host 2: kill -STOP <cloudstack-agent PID>. Wait until host 2 is Down (about 5 minutes). The router and VM P are shown Stopped and nics.broadcast_uri of their NICs on N is NULL; the domains are still running on host 2. 3. kill -CONT <cloudstack-agent PID>. Host 2 comes back Up, the events show "Out of band VM power on" for both, and they are Running. nics.broadcast_uri is still NULL. 4. Migrate the router (migrateSystemVm) and VM P (migrateVirtualMachine) to host 1. Both are refused with the error above. 5. Reboot the router and stop/start VM P. broadcast_uri is vlan://<vlan> again and the migration works. ### What to do about it? **Expected Result:** after "Out of band VM power on" the guest NICs carry the network's broadcast URI again, the same as after a normal start, so the VMs can be live migrated without a reboot or stop/start. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
