1.8 Virtualization Fundamentals
Key Takeaways
- A hypervisor creates and manages virtual machines on physical hardware (Type 1 runs on bare metal, Type 2 runs on an OS).
- Virtual machines (VMs) each run a full operating system and are isolated from each other.
- Containers share the host OS kernel and are lighter weight than VMs.
- Virtual switches (vSwitches) connect VMs to physical networks inside the hypervisor.
- Server virtualization reduces hardware costs, improves utilization, and enables rapid provisioning.
Virtualization Fundamentals
Virtualization is a core concept in modern networking. The CCNA tests your understanding of how virtualization works and its impact on network design.
What Is Virtualization?
Virtualization is the creation of virtual (software-based) versions of physical resources—servers, networks, storage. It decouples software from hardware, allowing multiple virtual systems to run on a single physical system.
Hypervisors
A hypervisor (also called a Virtual Machine Monitor or VMM) is software that creates and manages virtual machines on physical hardware.
Type 1 Hypervisor (Bare-Metal)
| Feature | Detail |
|---|---|
| Runs on | Directly on physical hardware (no host OS) |
| Performance | Near-native (minimal overhead) |
| Use case | Enterprise data centers, production workloads |
| Examples | VMware ESXi, Microsoft Hyper-V, KVM |
Type 2 Hypervisor (Hosted)
| Feature | Detail |
|---|---|
| Runs on | On top of a host operating system |
| Performance | Lower (host OS adds overhead) |
| Use case | Development, testing, learning labs |
| Examples | VMware Workstation, VirtualBox, Parallels |
Virtual Machines vs. Containers
| Feature | Virtual Machine (VM) | Container |
|---|---|---|
| Includes | Full OS + application | Application + libraries only |
| Isolation | Strong (separate OS kernel) | Process-level (shared kernel) |
| Size | Gigabytes (GB) | Megabytes (MB) |
| Startup time | Minutes | Seconds |
| Resource overhead | Higher | Lower |
| Portability | Good (VM images) | Excellent (container images) |
| Use case | Different OS types, strong isolation | Microservices, rapid scaling |
| Examples | VMware VMs, Hyper-V VMs | Docker, Kubernetes, Podman |
Virtual Networking
When you run VMs on a hypervisor, those VMs need network connectivity. This is handled by virtual switches (vSwitches) inside the hypervisor.
Virtual networking components:
- Virtual Switch (vSwitch): Software switch inside the hypervisor that connects VMs to each other and to physical network interfaces
- Virtual NIC (vNIC): Software network adapter assigned to each VM
- Port groups: Logical groupings on a vSwitch (similar to VLANs)
- Uplink: Connection from the vSwitch to a physical NIC on the host
How Virtual Networking Connects to the Physical Network
VM1 → vNIC → vSwitch → Physical NIC → Physical Switch → Network
VM2 → vNIC ↗
VMs on the same vSwitch can communicate without traffic ever leaving the physical host. Traffic between VMs on different hosts traverses the physical network normally.
Benefits of Virtualization for Networking
- Reduced hardware costs — multiple servers on one physical host
- Improved utilization — physical servers typically use 10-15% of capacity; VMs push this to 60-80%
- Rapid provisioning — spin up new servers in minutes, not weeks
- Simplified disaster recovery — VM snapshots, live migration
- Energy savings — fewer physical servers = less power and cooling
- Network simplification — fewer physical interfaces to manage
On the Exam: Understand the difference between Type 1 and Type 2 hypervisors, and know that VMs include a full OS while containers share the host kernel. Don't confuse them.
Which type of hypervisor runs directly on the physical hardware without a host operating system?
What is the primary difference between virtual machines and containers?