Good day. Further checking, please refer to below information :
1. If I'm working with untagged traffic, is it possible to work with VFs in port-trunking mode? isn't there a possibility for a loop in that case?
If it's possible, is there any configuration that should be done in the level of VFs or L2 classifier?
Ans: 82599 does not support port trunking mode.
2. is it possible to move a multi-cast from one VF to another on the same PF? is there a configuration needed for that sake?
Ans: Endpoint must register an IP multicast address to get multicast traffic. I believe VFs can register Multicast addresses. It's is
limited to 32 multicast addresses for all VF in the system.
3. Is STP protocol supported when working with VFs?
Ans: STP protocol is a switch protocol. This should be part of the kernel bridge feature.
4. Is it possible to start a VM which I attached a VF to, if the PF of this VF is down? (down in ifconfig terms)
Ans: No. PF need to be up in order for the VF to receive packets. It must be in up and active state for the traffic to flow from VFs.
Hope the above clarifies.