Compare and contrast architecture devices, their functions, and features: CompTIA A+ 220-901 sub-objective 2.8

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Detailed (and official) description of CompTIA A+ sub-objective 2.8

A+ Sub-objective 2.8: “Compare and contrast network architecture devices, their functions, and features”
> Hub
> Switch
> Router
> Access point
> Bridge
> Modem
> Firewall
> Patch panel
> Repeaters/extenders
> Ethernet over Power
> Power over Ethernet injector

Welcome to CertBlaster in this session we will look at 220-901 Sub-objective 2.8 Compare and contrast network architecture devices, their functions, and features. We will look at the evolution of interconnectivity and the roles these devices play in the grand scheme of things.


photo of a network hub

The smallest network you can create is a one to one (Peer to Peer) relationship between two computers or devices. A hub is designed to distribute multiple signals to multiple hosts, communications are managed by CDMA (Carrier Sense –Multiple Access) where a host will check the cable to see if it is clear before transmission is initiated. When a signal is distributed by a hub it is sent to all connected devices causing a burst of communications if left unchecked (CDMA).


Here is an example of really precise cable routing and management of four switches in a well-kept server space. Most installations start out like this.

Patch panel

Cable management is always important. It is especially important when there are a large number of users assigned and the cable closet is not particularly roomy. The purpose of a patch panel is to connect and manage inbound and outbound cables in a central area. Typically the destination would be labeled on the panel and lead to a wall jack. We have included possibly the nearest or certainly a best practices patch panel. Take a good look.

photo of a server rack
Patch Panel

But after a year or so of move/add/change, they will look more like this. Don’t worry the tech will be extricated shortly after the close of business (PST) when the fewest users will be impacted.

A switch determines whether or not a destination Hardware (MAC) or network (IP) address is attached to the switch itself and if not uses the MAC or IP addressing knowledge about the devices connected to it and the device oriented environment it exists in. Switches use packet switching, the information contained in each packet, to determine if the destination for the packet is connected locally or needs to be forwarded upstream. Unlike a hub, a switch uses the information gained. Switches operate as MAC Bridges. The goal of a switch is to enable efficient traffic management.

Now here they all are rolled into one device! Most reputable ISPs provide a device like the one shown. For this image we took the most fully featured non-ISP related modem available. My guess is that most of you have seen a variation of this in your travels. This device is a Cable Modem, a Router, a Firewall and a Wireless Access Point, this is of course including its roles as a Switch/Bridge.

Router /Access Point

photo of a wireless router for A+ exam sub-objective 2.8
Wireless router

Consider the Router as your network traffic cop. Ultimately it decides which traffic does and does not get on to your network, in conjunction with the Firewall which has the last word. The router is quite useful finding the quickest path for your data to take while finding its way through the maze of routers and servers from point to point. Shown here is a combination Router/ Wireless Access Point among other things it is responsible for routing and also access to the Wireless Network.


Just to digest the function of a bridge, here is a diagram. Which in this case takes the digital signal from the Wireless environment and converts it for use with a wired entertainment component.

Schematic of a network bridge diagram
Bridge diagram



When one thinks of a modem the traditional Digital to analog phone modem, where thus signal is converted from digital to analog on the opposite end. Shown here. The device can be internal.

photo of a Phone Modem RJ-11
Phone Modem RJ-11

Over the past few years the term became synonymous with Cable Modems. Cable Modems or Fiber modems are in the forefront of modems in use today. Most ISP provided modems today have port forwarding/ triggering functionality as well. This all-in-one feature bundling is part of the appeal of these devices. You no longer need a separate WAP, DHCP sever and Modem. Depending on the modem itself you may find a fully configurable Router and Firewall. The trend is towards having all services coming in on a single connection. (Show Router Access Point.jpg) Many readers have or have had this device in their homes. Cisco and Linksys


Firewalls can be     a hardware device, software or both. Naturally you can address more situations with the combination approach using your hardware to prevent threats as the first line of defense. Then secondarily your software firewall will provide additional protection and possibly even malware scans.

schematic of computer network firewall

The hardware firewall device’s placement is important. It should be between the external network, in most cases the internet, and your private network or LAN.




Digital audio information is represented on a sine wave display as a series of squared off steps, like a staircase. If displayed in the analog format would represent the same information as a smooth vertical line, a peak followed by decay back to zero. sine-square Here is the simplest display of this process

Since the PC is transmitting information digitally the signal can be refreshed and restored to its original state using a repeater or extender without changing. Using this method with an analog signal would boost the unwanted noise level along with the desired signal.

Ethernet over Power – EOP

There are two conceptually similar but vastly different technologies here. Your objectives call for The Ethernet over Power (EOP) technology. This type of power distribution allows for energy and Ethernet to share the same cabling. This allows for communication, command and control signals to be sent along with the main power supply.

Power over Ethernet- PoE

The PoE (Power over Ethernet) system reverses this existing technology using Ethernet cable as its primary carrier.  This impacts the effective Volt/Amp delivery as the RJ grade cable is not rated to carry the higher voltages some devices require. It is however ideal for a low voltage operation like a security monitor, or a baby monitor.

photo of a Phone over Ethernet connection
Phone over Ethernet – Upside down!

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That will do it for Sub-objective220-901 2.8! Good Luck on the test!!

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