Why Proxmox VMs Lose Network After Installing RKE2 on the Host

When Your Proxmox VM Gets No IP and Kubernetes Is the Culprit

I was setting up new VMs on my Proxmox homelab. Standard stuff, bridged networking on vmbr0, DHCP enabled, expected an IP in seconds. Instead, nothing. Just a link-local IPv6 address and eth0 with no IPv4.

The culprit in both cases was Calico, the CNI running inside my RKE2 cluster on the same Proxmox host. The two VMs hit the same root cause but through different network paths, which made the second one slightly more interesting to debug.

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Here is the full story of both.

My Setup

I run RKE2 directly on my Proxmox host (AMD Ryzen 9 9950X, 64GB RAM). The cluster hosts my SUSE AI stack, Open WebUI, Milvus, Ollama, using the RTX 5060 Ti on the host for GPU inference. The Proxmox host also runs regular KVM VMs bridged via vmbr0.

The bridge config in /etc/network/interfaces looks like this:

iface nic0 inet manual
auto vmbr0
iface vmbr0 inet static
    address 192.168.90.100/23
    gateway 192.168.90.1
    bridge-ports nic0
    bridge-stp off
    bridge-fd 0

Clean setup. Has worked fine for other VMs.

The Symptom