Thanks for the tips ! But I won't be using it, changing all the containers and VM network configuration will be to much work and change in our infrastructure (~250 containers and VM on ~8 proxmox server). It is much easier to modify the proxmox...
Update : The network issue comes from IPv6 Router Advertisements that is in Proxmox v9.
The containers automatically receive a public IPv6 address and a default IPv6 route from our provider network, and since Linux prefers IPv6 by default, all...