Virtual Networking Concepts

Virtualization allows a single physical machine (known as the host operating system) to run multiple virtual machines (known as the guest operating systems).

Advantages:

Server consolidation.
The ability to migrate virtual systems between different hardware
Centralized management of multiple systems.
Increased utilization of hardware resources.
Isolation of systems and applications.

Disadvantages:

A compromise in the host system could affect multiple guest systems.
A failure in a shared hardware resource could affect multiple systems.

Virtualization Components

Definition

Host Machine (physical server): The Machine that runs a virtual machine.

It shares its hardware with virtual machines so they can run, and this is managed by the Hypervisor.
- Shares: Hard disk drive(s), Optical Drive, RAM, CPU(s), NIC(s)
A host machine can handle as many Virtual machines as its hardware allows.

Hypervisor: A thin layer of software that resides between a virtual machine and the hardware.

It allows a virtual machine to interact with the Host OS hardware without interacting with the Host OS.
Manages CPU, Storage, and RAM

Types of hypervisors:

Type 1: Acts as an operating system on a physical machine (called bare metal)
Type 2: Acts as a software application that is run within a Host OS. It's basically an OS within an OS. You can run multiple at a time as long as you have the resources.

Type 1 hypervisors:

VMware Workstation and ESXi (made by VMware)Hyper-V (made by Microsoft)
XEN (open source)

Type 2 hypervisors:

VM Player (VMware)
VM Workstation (VMware)
Hyper-V (Microsoft)
Virtual Box (Oracle)

Virtual Machine: A software implementation of a computer that executes programs as a physical machine dos. It's self contained and autonomous. It can be run on a host server (Large scale, enterprise level) or a PC (Small scale).

Virtual Hard Disk (VHD): is a file created within the host operating system that simulates a hard disk for the virtual machine.

Types of Virtualization

Full Virtualization

The virtual machine completely simulates a real physical host. It's basically your PC creating a mini PC with a slice of its resources. (Most common type of VM)

Partial Virtualization

The virtual machine simulates some of the host OS's hardware and directly utilizes other parts. Instead of being able to use any OS and act like a computer, it must use an OS modified to do partial virtualization.

Paravirtualization.

The virtual machine does not simulate the hardware. The guest OS running on the hypervisor directly accesses the host hardware, and similarly uses a modified OS for paravirtualization.

Virtual Networking Explained

Virtual Servers

Virtual Servers allow for multiple instances of a server operating system to be run on a single PC.

A server that only runs on older hardware could be upgraded to run on a new computer virtualizing older hardware. (Ex. Server can only run on windows XP, you could virtually run windows XP on a windows 10 computer.)
You can also add a virtual server on a PC that has unutilized hardware resources in order to better utilize resources throughout a business.

Virtual Networking

Allows Virtual Servers and Virtual Desktops to communicate.

It also allows them to communicate with other devices on the physical network
VSwitches can exist as software or can exist as firmware built into the hypervisor.
They work the same as a physical switch.
They can be configured to route internally (only between VM's), or externally (VM's with physical devices).

Virtual Desktops

Also known as VDI (Virtual Desktop Interface).

Allows making multiple virtual desktops would allow a software developer to test his or her code on different platforms (I.E Windows, Linux, MacOS, Etc.)
You can also run virtual desktops on a powerful server and have users remote connect to the server to use these resources on low end PC's.

Virtual NICs

Within each virtual machine, you can configure one or more virtual network interfaces, which function similarly to physical network interfaces.

Multiple NICs can be added to a virtual machine.
Virtual NICs need the appropriate driver to function

Virtual Firewall

Virtualized hosts are susceptible to the same network exploits as physical network hosts and need to be protected by a firewall.

Implement a virtual firewall within the hypervisor itself to monitor and filter traffic on the virtual network as it flows between virtual machines
(VM-to-VM traffic monitoring).

Virtual Routers

Virtual Routers are like routers, except they can support multiple networks on each router interface, while a real router can only support 1 network on each.

Different routing tables are used on each network.
Multiple Virtual Networks can exist on the same Physical network

Virtual LANs

VLANs can be defined within a switch, and specific hosts can be assigned to a VLAN.

VLAN information can be trunked from the virtual switch to switches on the physical network,
This allows devices from VM's and real life to be added to the same VLAN

Jumbo Frames

Jumbo frames are Ethernet frames with more than 1500 bytes of payload. Jumbo frames can carry up to 9000 bytes of payload, but variations exist.

Virtual Networking Practice

Answer

Virtual OS1 Can communicate with:

Virtual OS3
Physical OS1
Physical OS2
Physical OS3
Physical OS4

This is because of port 5. As you can see, virtual network #1 and Physical network are both in that VLAN, meaning that any Virtual OS's assigned to Virtual Network #1 would be able to communicate with the Physical PC's, while any Virtual OS in Virtual Network #2 would not be able to.

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