CompTIA® Network+ Exam Notes : Virtualization And Network Storage Technologies

2. Infrastructure

2.4 Virtualization and network storage technologies

Virtualization is the creation of a virtual rather than actual version of something, such as an operating system, a server, a storage device or network resources.

Virtual Networking Components:

Virtual Switch: A virtual switch is a software program that allows one virtual machine (VM) to communicate with another. Like a physical switch, a virtual switch connects networking components together. Virtual switches, which are also referred to as virtual networks, are named VMnet0, VMnet1, VMnet2, and so on.

Virtual Firewall: A virtual firewall (VF) is a network firewall service or appliance running entirely within a virtualized environment and which provides the usual packet filtering and monitoring provided via a physical network firewall.

Virtual NIC: Virtual Network Adapter is a program (instead of a physical network adapter) that allows a computer to connect to a network. A virtual network adapter can also be used to connect all the computers on a local area network (LAN) to a larger network such as the Internet or a collection of LAN.

Virtual Router: Virtual router is a software-based routing framework that allows the host machine to perform as a typical hardware router over a local area network. A virtual router can enable a computer/server to have the abilities of a full-fledged router by performing the network and packet routing functionality of the router via a software application. Virtual Router Redundancy Protocol (VRRP) may implement virtual routers to increase the reliability of the network. This is done by advertising a virtual router as the default gateway, backed by a group of physical routers.

Hypervisor: A hypervisor is a function which abstracts -- isolates -- operating systems and applications from the underlying computer hardware. This abstraction allows the underlying host machine hardware to independently operate one or more virtual machines as guests, allowing multiple guest VMs to effectively share the system's physical compute resources, such as processor cycles, memory space, network bandwidth and so on. A hypervisor is sometimes also called a virtual machine monitor.

Network Storage types:

NAS: A network-attached storage (NAS) device is a server that is dedicated to nothing more than file sharing. NAS does not provide any of the activities that a server in a server-centric system typically provides, such as email, authentication or file management. A network access server (NAS) is a computer server that enables an independent service provider (ISP) to provide connected customers with Internet access. A network access server has interfaces to both the local telecommunication service provider such as the phone company and to the Internet backbone.

SAN: A storage-area network (SAN) is a dedicated high-speed network (or subnetwork) that interconnects and presents shared pools of storage devices to multiple servers.

Software Defined Network will allow the administrator to implement features and functions and configurations without the need to do the individual command-line configuration on the network devices.

SCADA/ICS systems are often used to gather and analyze data from remote systems in real time.

Connection Type:

FcoE: It stands for Fibre Channel over Ethernet. It solves the problem of organizations having to run parallel network infrastructures for their local area networks (LANs) and their storage area networks (SANs). As a result, they have to operate separate switches, host bus adapters (HBAs), network interface cards (NICs) and cables for each of these networks.

Fibre Channel, or FC, is a high-speed network technology (commonly running at 2-, 4-, 8- and 16-gigabit per second rates) primarily used to connect computer data storage.

While Ethernet-based standards and protocols are extremely fast, the InfiniBand protocols reduce the workload on server OSs and hardware. This results in faster data transfers with considerably lower latencies. The best choice is therefore InfiniBand.

Fibre Channel over Ethernet (FCoE) developed by Cisco. The main application of FCoE is in data center storage area networks (SANs).

Fiber channel utilizes FCP (Fibre Channel Protocol ) transport protocol that transports SCSI commands over Fibre Channel networks.

ISCSI: ISCSI is a way of connecting storage devices over a network using TCP/IP. It can be used over a local area network (LAN), a wide area network (WAN), or the Internet. iSCSI devices are disks, tapes, CDs, and other storage devices on another networked computer that you can connect to.

LUN (logical unit number): It is a number used to identify a logical unit, which is a device addressed by the SCSI protocol or Storage Area Network protocols

Fibre Channel, or FC, is a high-speed network technology (commonly running at 2-, 4-, 8- and 16-gigabit per second rates) primarily used to connect computer data storage.

Differentiated Services Code Point (DSCP) is a field in an IP packet that enables different levels of service to be assigned to network traffic.

Jumbo Frame: A jumbo frame is an Ethernet frame with a payload greater than the standard maximum transmission unit (MTU) of 1,500 bytes. Jumbo frames are used on local area networks that support at least 1 Gbps and can be as large as 9,000 bytes. These jumbo frames are sometimes also called "Giants".

Example: You are consulted to plan an internetwork for an organization. How will you determine the number of host IPs' you will be requiring for the proposed internetwok?

Total Number of host IPs' required = One for each NIC (Network Interface Card) + One for each interface on routers.


For routing between two subnets, you need two network cards (NICs). A computer with two or more NICs is called a multi-homed computer. Further, you need to enable IP forwarding, so that packets from one subnet are forwarded to the other subnet as required.

Firewall is an optional software/hardware component, and it mainly intended to restrict packet forwarding according to a preset criteria.

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