No network access until "ip link set"

[ocroquette]

Hi,

recently, I had several cases where a VM (created from a template) had no network access unil I ran "ip link set" on the host. Until I came to the idea to do that, I did:
- changed the bridge of the network interface of the VM settings
- removed the network interface of the VM to recreate it
- check the interface from the host - everything was fine. Except no traffic in or out
- check the output of "brctl show". The network interface of the VM was correctly shown

Nothing helped, but "ip link set".

Now that I know the workaround, it is not so bad, but it would be even better not to have the issue. Do you have any idea what could be causing this?

 

[ocroquette]

Follow-up: after I use "ip link set", the firewall rules are ignored. So maybe my problem is not relatated to the network interface, but to the firewall. But even disabling the firewall for the impacted VM does not enable network traffic. Only "ip link set" does.