CompTIA A+ Rapid Review: Networking

  • 4/15/2013

Objective 2.9: Compare and contrast network devices and their functions and features

Computers and printers within a network are connected to various network devices such as hubs, switches, routers, access points, bridges, and modems. This objective expects you to know the functions and features of each of these network devices.

Exam need to know...

  • Hub

    For example: What is the difference between a hub and a switch?

  • Switch

    For example: What are benefits of switches over hubs?

  • Router

    For example: What additional protocols are often included on routers used in SOHOs?

  • Access point

    For example: What is the difference between a WAP and a wireless router?

  • Bridge

    For example: What is the difference between a bridge and a switch?

  • Modem

    For example: What type of connector does an internal modem use?

  • NAS

    For example: What is the primary purpose of a NAS?

  • Firewall

    For example: What is created on a firewall to allow traffic through?

  • VoIP phones

    For example: What type of calls can be made with VoIP phones?

  • Internet appliance

    For example: What is the purpose of an Internet appliance?


A hub is a simple network device used to connect multiple devices together in a network. Ethernet hubs were once very common. They have multiple RJ-45 ports, which were connected to computers or other network devices via twisted-pair cable.

True or false? A hub sends unicast traffic that it receives to all other devices that are connected to the hub.

Answer: True. A hub transmits all data that it receives on one port to all other ports.

When looking at the features of various network devices, it’s valuable to know the difference between unicast, broadcast, and multicast traffic, as follows:

  • Unicast traffic is sent from one device and addressed to one other device. Even though unicast traffic is addressed to only one device, the hub still forwards unicast traffic to all other devices connected to the hub.

  • Broadcast traffic is sent from one device to all other devices on a network. Broadcast traffic is not sent through a router.

  • Multicast traffic is sent from one device to multiple other devices.

True or false? A hub has the most security when compared to a switch.

Answer: False. A hub has less security than a switch.

If sensitive data is sent to one port on the hub, it is automatically sent to all other ports. Any computer connected to the hub will receive this data and can intercept it with the right tools. In contrast, a switch forwards unicast traffic to only one port.


A switch includes circuitry that allows it to be selective when sending data through the switch. It can identify which device is connected to each physical port, based on the media access control (MAC) address.

True or false? A switch sends unicast traffic to a single physical port.

Answer: True. A switch transmits data that it receives to specific ports. It analyzes packets to determine the destination MAC address and sends the packet to the port where that MAC address is being used.

Switches learn which devices are connected to which physical port by analyzing traffic that comes into the port. They build an internal table mapping the physical port number with the MAC address. They then send unicast traffic only to the specific port where the MAC address is used.

In contrast, a hub forwards traffic to all other ports on the hub. The selectivity of the switch provides better performance for devices connected to the switch. Additionally, the switch adds some security by not sending unicast traffic to all ports.


Routers are used to connect networks or subnets together. In general, the networking devices are connected together with a switch or a hub in a network, and multiple networks are connected together with a router. Routers evaluate the IP address of traffic and determine the best path to send it to get it to its destination. Each router in a path is also referred to as a hop.

True or false? A router is placed between an internal network and the Internet.

Answer: True. Routers connect networks, and in this case, the internal network is one network and the Internet is a huge network of networks.

Routers placed between the Internet and an internal network commonly uses network address translation (NAT). NAT translates private IP addresses used internally, within a network, to public IP addresses used on the Internet.

A company could have multiple routers, with some used to connect internal networks and another one used to connect to the Internet. The internal routers would not use NAT.

Access point

A wireless access point (WAP) is sometimes referred to as simply an access point. It provides access for wireless clients to a network.

True or false? Wireless access points provide the same services as a wireless router.

Answer: False. A router provides more services than a mere access point.

A wireless access point and a wireless router are not the same things. Specifically, an access point provides connectivity only for wireless clients to other wireless clients and to a wired network. However, a wireless router includes multiple other components.

Figure 2-3 shows the components of a typical wireless router. It has RJ-45 connections for wired clients and wireless capabilities for wireless clients. These wired and wireless clients are connected to each other using the switch component of the wireless router. The wireless router has a wide area network (WAN) connection used to connect to the Internet, and all of the clients can go through this router for Internet access.

Figure 2-3

Figure 2-3 Wireless router.


A bridge is similar to a switch but instead of connecting individual devices, it’s used to connect groups of devices. For example, two groups of computers might be connected to each other with two separate hubs. You can then use a bridge to connect the two groups together via the bridge. Even though the two groups are connected, the bridge is selective about what data is forwarded between the two groups of devices.

True or false? Bridges are used instead of switches in most networks today.

Answer: False. Bridges are rarely used. When the functionality of a bridge is needed, switches are typically used instead.


Modems are used for Internet access connections for a computer via a phone line. They use RJ-11 connections to connect to the phone line. Many modems are internal to a computer, but external modems are also available. An external modem typically connects to a computer with a USB connection.

True or false? A modem converts digital signals to analog signals.

Answer: True. A modem converts digital signals coming from a computer to analog signals that can be transmitted on a phone line.

The analog signals are modulated by the modem before being placed onto the phone line. The modem is also able to demodulate received data to convert the analog data into digital data needed by the computer.


Network attached storage (NAS) is a dedicated computer system used to provide disk storage on a network. A NAS device includes one or more disk drives, and storage sizes of 1 TB or greater are common. They have RJ-45 ports used to connect a twisted-pair cable to a switch or router on a network.

True or false? NAS devices do not have any security, so sensitive data should never be stored on the NAS.

Answer: False. NAS devices include an operating system that can be used to assign permissions and restrict access to folders.

Many NAS devices use Unix or Linux as the operating system and require very little configuration or management. They often include a web-based interface that you can use to create additional users, groups, and folders, and to assign permissions to the folders. In addition to using NAS devices to share data, many people use them to store backups.


A firewall filters traffic in and out of a network or in and out of an individual computer. Firewalls are generally classified as either network-based or host-based. A network-based firewall is often used in conjunction with a router to filter traffic in and out of a network. A host-based firewall is additional software running on a computer for additional security protection.

True or false? Firewalls can block outgoing email by blocking traffic on port 25.

Answer: True. Firewalls can filter traffic based on ports. Port 25 is used for outgoing email, so if this port is not open on the firewall, it will block outgoing email.

Firewalls can also filter traffic based on IP addresses, network IDs, and protocols with simple packet filtering. Most firewalls also support more advanced filtering, allowing them to analyze traffic to determine whether the data should be allowed or blocked.

Most firewalls use an implicit deny philosophy with exceptions. That is, all traffic is blocked (denied) unless a rule or exception has been created to allow it. For example, if you wanted to allow outgoing email, the firewall needs to have a rule opening port 25 for outgoing traffic.

VoIP phones

A Voice over Internet Protocol (VoIP) phone is used to make telephone calls over an IP network. They resemble a regular phone, but instead of plugging into a telephone line with an RJ-11 connector, they plug into a network device like a switch or router with an RJ-45 connector.

True or false? VoIP phones can be used instead of traditional phones for long distance calls.

Answer: True. As long as you have Internet access, you can use the VoIP phone to make telephone calls.

Internet appliance

Internet appliances are small devices used to access the Internet for web browsing or email access. Many of the features of an Internet appliance are included with mobile devices such as smartphones and tablets.

Can you answer these questions?

You can find the answers to these questions at the end of this chapter.

  1. What is a benefit of a switch over a hub?

  2. What type of network device would include NAT?

  3. What type of device is used to connect to a dial-up ISP?

  4. What type of device blocks all traffic unless a rule is created to allow the traffic?

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