Can't migrate VM in the Cluster from proxmox-6 to proxmox-8

[Gombert]

I have a free licence cluster running proxmox-6.2.1 for many years, composed of 3 nodes.
I have to upgrade to support newer containers.
So, i've migrate the vm from nodes3, "delnode" it from the cluster, install proxmox-8.3, configure network and joined it to the cluster.
I can create CT on the "new" nodes3 and tag it to different vlan to test proxmox config network. All seems to work fine.

But, I can't migrate vm from node1 or node2 to node3 : the message is :
TASK ERROR: command '/usr/bin/ssh -e none -o 'BatchMode=yes' -o 'HostKeyAlias=rtprox3' root@172.31.25.6 pvecm mtunnel -migration_network 192.168.0.4/24 -get_migration_ip' failed: exit code 255

From node3, I can ping the "2 ports 10G network interface" of node1 and node2 (192.168.0.x : the migration network)

Where is my mistake ?
Thanks for reading,

 

[fabian]

skipping a version like that is not supported and might have other problems as well.. the issue you are running into is a compatibility problem in a mixed-version cluster if you add *new* nodes as opposed to upgrading existing ones. you need to either upgrade the old nodes, or manually add the SSH key of the new node(s) to "/etc/pve/priv/known_hosts" to make them available to the old nodes.