I am a little bit further. Just enabling spanning tree portfast did the trick as far as the switches concerned.
I could enable both interfaces without killing my switched network.
I am now migrating the vlans to the LACP interface. I think I have 2 options:
Create new tagged vlan, assign interface and re-tag on all devices with the vlan tag (with this option I need to change the vlan tag on several devices) or….
Create new tagged vlan, delete interface, delete vlan, change vlan tag on newly created vlan to old one, and assign interface, but then I need to re-configure all the firewall rules and the interface, dhcp etc again.
I have one vlan which I would not like to re-tag on al my hypervisors etc. But I also would not like to create all firewall rules etc all over again.
What is the smartest way to migrate a vlan, with a lot of rules to the new LAGG interface, without changing the vlan id?
Thanks,
Mark