Allow additional allowed IPs for VMs in Security Group networks

### The required feature described as a wish

Hi,

I’m currently experimenting with Anycast for Kubernetes clusters.

For this setup, I have two BGP router VMs that talk to multiple tenant worker nodes. The worker nodes should be able to announce external IPs for Kubernetes LoadBalancer services.

The goal is to have multiple tenants on a shared L2 network and use Security Groups for isolation.

The issue is that CloudStack does not know about these external IPs in my scenario, so traffic gets blocked on the hypervisor iptables layer. As far as I understand it, only IPs that CloudStack knows about are allowed as destination IPs for a specific VM.

Even if I create a separate network containing those external IPs, I cannot assign the same IP to multiple VMs. Because of that, real Anycast is not possible.

What would be useful is a way to allow additional destination IPs for a VM or Security Group without requiring CloudStack to assign those IPs directly to a single VM. This would allow external systems, like Kubernetes with BGP-based LoadBalancer announcements, to handle the IP ownership dynamically while CloudStack still provides L2 isolation and anti-spoofing.

Commencez par examiner le comportement de Security Group et le filtrage iptables de l’hyperviseur décrits dans l’issue, en vous concentrant sur la manière dont les IP de destination sont actuellement autorisées pour les VM. Définissez comment des IP de destination supplémentaires pourraient être autorisées pour une VM ou un Security Group tout en préservant l’isolation L2 et l’anti-spoofing, puis vérifiez la conception par rapport au scénario Kubernetes BGP Anycast.

Rédigé par le modèle d'indexation à partir du texte de l'issue.