Virtualization

 

Virtualization refers to the practice of breaking down the physical infrastructure of computing and networking resources into smaller, reusable and more flexible units

 CCNP Enterprise blueprint which is Virtualization. Given how ubiquitous virtualization has become, this topic absolutely deserves a spot on a professional level networking certification exam. Undoubtedly at some point in your networking career you’ll come across virtual networking devices, probably sooner than later. But virtualization is not just about hypervisors and virtual machines, although that is part of it.

The Virtualization section is weighted at 10% of the overall exam. Let’s take a look!

2.1 Describe device virtualization technologies

• 2.1.a Hypervisor type 1 and 2
• 2.1.b Virtual machine
• 2.1.c Virtual switching

2.2 Configure and verify data path virtualization technologies

• 2.2.a VRF
• 2.2.b GRE and IPsec tunneling

2.3 Describe network virtualization concepts

• 2.3.a LISP
• 2.3.b VXLAN

Don’t let this topic overwhelm you and certainly don’t let it fool you. There are certainly some challenging concepts in here, so let’s break them down one by one.

A hypervisor is the platform that runs all the virtual machines. I like to use the analogy of a traffic cop. It directs the available resources and controls which virtual machines get access to which physical resources. There are two types of hypervisors –  a Type 1 and a Type 2. You may have used one or both of these and are not even aware of it. A Type 1 hypervisor is also known as a bare metal hypervisor because it sits closest to the hardware. Examples of Type 1 hypervisors are VMware’s ESXi and Microsoft’s Hyper-V, among others.

A Type 2 hypervisor on the other hand is an application installed on an operating system. Examples include VMware Workstation, or Fusion on the Mac, Oracle’s Virtualbox, and others. Type 2 hypervisors communicate with the host OS to negotiate and share physical resources between the host OS and the guest OS, or the VM (virtual machine).

The virtual machine is a virtual instance of a physical computer. It acts just like a physical machine in that it boots up, runs an operating system, has access to memory, CPU, network cards, and other resources allotted to it. And Virtual Switching works just like physical switching.

Virtualization in networking has been happening for a long time. Like VRF. A VRF or virtual routing and forwarding creates a virtual router instance, a completely separate routing table, on the router. This allows large enterprise or ISP networks to have overlapping IP ranges in various parts of the network, but restricts which networks can talk to each other, so the overlapping isn’t a conflict.

GRE Tunneling

GRE tunnels, and GRE tunnels wrapped in IPSec create virtual networks across the internet. While the packet may traverse the public internet and have its TTL decremented, any number of times a packet that traverses the tunnel only sees that as a single hop.

LISP and VxLAN, comparatively, are newer topics. However, their importance is becoming more and more significant and their usage more common and widespread. LISP, or Locator/ID Separation Protocol separates the association of subnets/prefixes with physical locations. So, an IP Address can be anywhere in the network. LISP, while powerful on its own, is one of the underlying technologies is Cisco’s SD-Access architecture, which is also a topic in itself on the new CCNP blueprint, more on that later though.

VxLAN

The same can be said for VxLAN – Virtual Extensible Local Area Network. In a nutshell VxLAN extends Layer 2 across Layer 3 boundaries but encapsulating the entire L2 Frame. One popular example is extending data center subnets across multiple data centers so services can exist in multiple physical locations. This makes it easier to failover services or provide high availability. Like LISP, VxLAN is also used is Cisco SD-Access architecture. You can also find VxLAN in Cisco’s Data Center SDN solution, ACI. In addition to be part of these solutions, VxLAN also stands very well on its own.