IT 3300 : Virtualization

Proxmox — Networking

The core idea: bridges

• A Linux bridge is a virtual switch inside the host
• vmbr0 is the default bridge, tied to a physical NIC
• VMs and containers attach to a bridge to reach the network

vmbr0 in plain terms

VMs talk to each other and out to the LAN through the bridge.

VLANs

• One physical link can carry many isolated networks via VLAN tags
• Put VMs on different VLANs for separation (e.g. public vs. private)
• Set the VLAN tag on the VM's network device
• Match the tag to your assigned switchport configuration

Public vs. private

• Some VMs need to be reachable from campus/internet (public VLAN)
• Others should be internal only (private VLAN)
• Plan which workloads go where before you build them
• Docker/k8s hosts often sit on the public VLAN in this course

The Proxmox firewall

• Built-in firewall at datacenter, node, and VM levels
• Default-deny where it matters; open only what you need
• Rules cascade — understand the order they apply

SDN (software-defined networking)

• Proxmox has built-in SDN for defining virtual networks centrally
• Zones, VNets, and subnets managed cluster-wide
• Useful as clusters grow beyond a single bridge
• Awareness for now; the bridge model covers our labs

Lab goals

• Confirm which physical port maps to vmbr0
• Place one VM on the public VLAN, one on a private VLAN
• Verify the private VM cannot be reached from outside