Networking Basics – My Knowledge Check (Answers)

Explanation: Hypertext Transfer Protocol (HTTP) and HTTP Secure (HTTPS) are two application layer protocols that manage the content requests from clients and the responses from the web server. HTML (Hypertext Mark-up Language) is the encoding language that describes the content and display features of a web page. DNS is for domain name to IP address resolution. DHCP manages and provides dynamic IP configurations to clients.

Explanation: When a wireless router is being set up, the default setting for the SSID Broadcast is enabled. This means the wireless router will broadcast the SSID to all devices. This can be a security concern and best practice is to disable the broadcast setting.

Explanation: IPv4 addresses in the address block 169.254.0.0 to 169.254.255.255 are link-local addresses. The operating system of a host can automatically assign an address from this block to the host in case no IP configuration is available. An example is when a host is configured to obtain a dynamic IP address but cannot reach any DHCP server during the boot process. In such a case, the operating system can assign a link-local address.

Explanation: Network media is a term used to describe the actual physical layer transport along the path over which an electrical signal travels as it moves from one component to another.

Explanation: When a web client visits a web server, several network communication protocols are involved. These different protocols work together to ensure that the messages are received and understood by both parties. These protocols include the following:
Application Protocol – governing the way a web server and a web client interact
Transport Protocol – managing the individual conversations between web servers and web clients
Internet Protocol – taking the formatted segments from the transport protocol, encapsulating them into packets, assigning them the appropriate addresses, and delivering them across the best path to the destination host
Network Access Protocol – preparing packets to be transmitted over the network media
Network Time Protocol is used to synchronize clocks between computer systems. It is not involved in this case.

Explanation: Wireless networks can be broadly classified as follows:

• Wireless wide-area network (WWAN) – It operates in the range of miles.
• Wi-Fi – It operates up to distances of 0.18 miles and provides network access to home and corporate users and can include data, voice and video traffic.
• Bluetooth – It uses a device-pairing process to communicate over distances of up to 0.05 miles.
• GPS – It uses satellites to transmit signals that cover the globe.

Explanation: DHCP is generally the preferred method of assigning IP addresses to hosts on large networks because it reduces the burden on network support staff and virtually eliminates entry errors. However, DHCP itself does not discriminate between authorized and unauthorized devices and will assign configuration parameters to all requesting devices. DHCP servers are usually configured to assign addresses from a subnet range, so there is no guarantee that every device that needs an address will get one.

Explanation: If the destination host is in the same LAN as the source host, there is no need for a default gateway. A default gateway is needed if a packet needs to be sent outside the LAN.

Explanation: The MAC address of PC3 is not present in the MAC table of the switch. Because the switch does not know where to send the frame that is addressed to PC3, it will forward the frame to all the switch ports, except for port 4, which is the incoming port.

Explanation: The address resolution protocol (ARP) maintains a cache of MAC to IPv4 address mappings on the local computer. If there is no mapping in the cache for a specific IPv4 address, then the ARP process sends an Ethernet broadcast on the local link in an attempt to resolve the destination IPv4 address to a MAC address.

Explanation: When Voice over iP (VoIP) is being used, analog voice signals are translated into digital data in the form of IP packets. This translation allows the phone call to be carried through a computer network.

Explanation: Peer-to-peer networks exist directly between client devices, with no centralized resources or authentication. Hybrid peer-to-peer systems also exist that decentralize resource sharing but can use centralized indexes to point to the resource locations.

Explanation: IPv4 addresses are 32-bit (4 octets) long. IPv4 addresses are logical addresses and are assigned to host network interfaces as needed. IPv4 addressing is hierarchical and each IPv4 address is made up of two parts, the network number (or network address) and the host number. IPv4 addresses are used both on local networks and on the internet.

Explanation: When a router receives a frame on an interface, it strips the Layer 2 frame header information from the frame. It checks the routing table to determine which interface to use to send the packet to its destination. Once the interface is known, the packet is encapsulated with a new frame header containing different source and destination MAC addresses.

Explanation: When a client is initiating a request to open an FTP session, it does so by sending a packet to the FTP server with the destination port 21.

Explanation: Routers break networks into separate broadcast domains. Each LAN is a broadcast domain. The correct answer has only one broadcast domain. All other answers have two broadcast domains.

Explanation: In the segment between R2 and the web server, when R2 encapsulates a frame to be sent to the web server, R2 uses the MAC address of its interface that is directly connected to the segment, Fa0/1, as the source MAC.

Explanation: There are a number of reasons to use routers to divide a network into smaller segments. Expanding the network into a different geographic location may require the use of routers at both locations. Another reason is to limit broadcasts that must be processed by all devices on the network segment. Routers do not forward broadcast traffic off the local network segment.

Explanation: Both UDP and TCP use port numbers to provide a unique identifier for each conversation. Source port numbers are randomly generated and are used to track different conversations. Destination port numbers identify specific services by using either a default port number for the service or a port number that is assigned manually by a system administrator.

Explanation: When the client receives the DHCPOFFER from the server, it sends back a DHCPREQUEST broadcast message. On receiving the DHCPREQUEST message, the server replies with a unicast DHCPACK message.

Explanation: Standards ensure that different devices connecting to the network are able to communicate with each other. In networking there are many standards that define how the network should operate and that all components implement the same protocols.

Explanation: MAC address filtering uses the MAC address to identify which devices are allowed to connect to the wireless network.

Explanation: All communication methods include a message source, destination, and a transmission medium.

Explanation: There are two rules to help reduce the notation of IPv6 addresses. The first one is to omit any leading 0s (zeros) in any hextet. The second one is that a double colon (::) can replace any single, contiguous string of one or more 16-bit hextets consisting of all zeros, but the double colon (::) can only be used once within an address. If an address has more than one contiguous string of all-0 hextets, the best practice is to use the double colon (::) on the longest string. So, applying the first rule in the IPv6 address we have 2001:db8:0:0:ab00:0:0:0, and applying the second rule results in 2001:db8:0:0:ab00::

Explanation: Home users will go online shopping over the Internet because online vendors are accessed through the Internet. An intranet is basically a local area network for internal use only. An extranet is a network for external partners to access certain resources inside an organization. A home user does not necessarily need a LAN to access the Internet. For example, a PC connects directly to the ISP through a modem.

Explanation: The DNS server resolves Internet names to associated IP addresses.

Explanation: The Hypertext Transfer Protocol (HTTP) provides services between a web browser requesting web pages and a web server responding to the requests. HTML (Hypertext Markup Language) is a markup language to instruct a web browser how to interpret and display a web page.

Explanation: The simplest peer-to-peer network consists of two computers that are directly connected to each other through the use of a wired or wireless connection. The advantages of peer-to-peer networking include ease of setup, lower cost, and less complexity.

Explanation: A directed broadcast is a message sent to all hosts on a specific network. It is useful for sending a broadcast to all hosts on a nonlocal network. A multicast message is a message sent to a selected group of hosts that are part of a subscribing multicast group. A limited broadcast is used for a communication that is limited to the hosts on the local network. A unicast message is a message sent from one host to another.

Explanation: The TCP/IP internet layer provides the same function as the OSI network layer. The transport layer of both the TCP/IP and OSI models provides the same function. The TCP/IP application layer includes the same functions as OSI Layers 5, 6, and 7.

Explanation: Routers do not forward broadcasts to other networks. Routers examine broadcasts to determine if they need to act on the broadcast, such as an ARP request or a DHCP DISCOVER message. If the router does not need to respond to the broadcast, it is dropped.

Explanation: When a host uses DHCP to automatically configure an IP address, the typically sends two messages: the DHCPDISCOVER message and the DHCPREQUEST message. These two messages are usually sent as broadcasts to ensure that all DHCP servers receive them. The servers respond to these messages using DHCPOFFER, DHCPACK, and DHCPNACK messages, depending on the circumstance.

Explanation: Pairing describes connecting two devices using Bluetooth. Syncing Is the term used to describe synchronizing emails and calendars across a number of devices.

Explanation: Network Address Translation (NAT) can allow a large group of privately addressed hosts to share one or more registered public IP addresses in order to route packets over the internet.

Explanation: A device needs an IP address in order to connect to a network. A device that is attached to a networked device can use the established connection to access the network.

Explanation: The IP address design being used is by geographic location (for example, one campus is 10.1, another campus 10.2, another campus 10.3). The other design criterion is that the next octet number designates IP phones, or a specific device type, with numbers starting with 4, but which can include other numbers. Other devices that might get a designation inside this octet could be printers, PCs, and access points.

Explanation: IPv6 addresses are represented by 32 hexadecimal digits (0-9, A-F). The size of the notation can be reduced by eliminating leading zeroes in any hextet and by replacing a single, contiguous string of hextets containing all zeroes with a double colon, which can only be used one time.

Explanation: Optical fiber cable transmits data over longer distances and at higher bandwidths than any other networking media. Unlike copper wires, fiber-optic cable can transmit signals with less attenuation and is completely immune to EMI and RFI.

Explanation: UDP is not a connection-oriented protocol and does not provide retransmission, sequencing, or flow control mechanisms. It provides basic transport layer functions with a much lower overhead than TCP. Lower overhead makes UDP suitable for applications which are sensitive to delay.

Explanation: A Layer 2 switch determines how to handle incoming frames by using its MAC address table. When an incoming frame contains a destination MAC address that is not in the table, the switch forwards the frame out all ports, except for the port on which it was received.

Explanation: Actuators are a type of device that is used to produce physical movement.

Explanation: An intermediary device sends network messages toward a final destination. Examples of intermediary devices include a firewall, router, switch, multilayer switch, and wireless router.

Explanation: Logical addresses, also known as IP addresses, are added at the network layer. Physical addresses are edded at the data link layer. Port addresses are added at the transport layer. No addresses are added at the physical layer.

Explanation: 900 MHz is an FCC wireless technology that was used before development of the 802.11 standards. 900 MHz devices have a larger coverage range than the higher frequencies have and do not require line of sight between devices. 802.11b/g/n/ad devices all operate at 2.4 GHz. 802.11a/n/ac/ad devices operate at 5 GHz, and 802.11ad devices operate at 60 GHz.

Explanation: The subnet mask determines which part of the IP address is the network number. Because the subnet mask is 255.255.255.0, the first three sets of numbers in each IPv4 address indicate the network number. IPv4 addresses with the same network number are considered in the same local network.

Explanation: The reserved private IPv4 network addresses include 10.0.0.0 to 10.255.255.255, 172.16.0.0 to 172.31.255.255, and 192.168.0.0 to 192.168.255.255.

Explanation: Broadcast communications on a network may be directed or limited. A directed broadcast is sent to all hosts on a specific network. A limited broadcast is sent to 255.255.255.255. When a DHCP client needs to send a DHCP Discover packet in order to seek DHCP servers, the client will use this IP address of 255.255.255.255 as the destination in the IP header because it has no knowledge of the IP addresses of DHCP servers.

Explanation: When a router receives a packet, it examines the destination address of the packet and uses the routing table to search for the best path to that network.

Explanation: The purpose of an ARP request is to find the MAC address of the destination host on an Ethernet LAN. The ARP process sends a Layer 2 broadcast to all devices on the Ethernet LAN. The frame contains the IP address of the destination and the broadcast MAC address, FFFF.FFFF.FFFF. The host with the IP address that matches the IP address in the ARP request will reply with a unicast frame that includes the MAC address of the host. Thus the original sending host will obtain the destination IP and MAC address pair to continue the encapsulation process for data transmission.

Explanation: Encapsulation is the process of placing one message format into another message format. An example is how a packet is placed in its entirety into the data field as it is encapsulated into a frame.

Explanation: Bluetooth is a low-power, short range wireless technology that provides connectivity for accessories such as speakers, headphones, and microphones.

Explanation: A wireless router connects multiple wireless devices to the network. It will then aggregate the internet access requests from home devices to the internet.

Explanation: Hypertext Transfer Protocol (HTTP) is a protocol that is used by web servers to serve up a web page.

Explanation: Command bandwidth measurements are as follows from smallest to largest:

1. Thousands of bits per second (Kbps) or Kilobits per second
2. Millions of bits per second (Mbps) or Megabits per second
3. Billions of bits per second (Gbps) or Gigabits per second
4. Trillions of bits per second (Tbps) or Terabits per second

Explanation: Fiber optic cable can deliver signals over distances of several miles. Because it uses light, fiber is impervious to RFI and EMI and is superior to signals sent over copper or aluminum wiring.

Explanation: All network devices must have an IP address to communicate on the network. The IP address is used to uniquely identify each device on the network.

Explanation: The simplest form of peer-to-peer networking consists of two computers that are directly connected to each other through the use of a wired or wireless connection.

Explanation: The subnet mask is used to determine which part of the IPv4 address is the network number. Because the subnet mask is 255.255.255.0, the first three sets of numbers in an IPv4 address indicate the network number.

Explanation: When used by itself (without any options), the netstat command will display all the active TCP connections that are available.

Explanation: The private IP address blocks that are used inside companies are as follows:10.0.0.0 /8 (any address that starts with 10 in the first octet)
172.16.0.0 /12 (any address that starts with 172.16 in the first two octets through 172.31.255.255)
192.168.0.0 /16 (any address that starts with 192.168 in the first two octets)

Explanation: The TCP/IP model consists of four layers: application, transport, internet, and network access. The OSI model consists of seven layers: application, presentation, session, transport, network, data link, and physical. The top three layers of the OSI model: application, presentation, and session map to the application layer of the TCP/IP model.

Explanation:Command bandwidth measurements are as follows:

• Thousands of bits per second (Kbps) or Kilobits per second
• Millions of bits per second (Mbps) or Megabits per second
• Billions of bits per second (Gbps) or Gigabits per second
• Trillions of bits per second (Tbps) or Terabits per second

Explanation: Bluetooth is a wireless technology that uses the 2.4 GHz frequency to connect peripheral devices over a short-range, low-speed connection.

Explanation: The hexadecimal numbers are 0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f. The hexadecimal number 0 represents 0 in decimal and is represented as 0000 in binary. The hexadecimal number f represents 15 in decimal.

Explanation: DHCP servers can be computers or networking devices that are configured to assign IPv4 addresses to network connected devices.

Explanation: GPS, or Global Positioning System, provides the geolocation services used by smartphones to calculate the position of the phone.

Explanation: Radio-frequency identification (RFID) tags use electromagnetic fields to identify and track objects.

Explanation: An IPv6 address is comprised of 128 bits as opposed to 32 bits in an IPv4 address. Thus it offers far more addresses for networks and hosts than an IPv4 address does.

Explanation: The ports shown in the diagram are used as follows: The LAN ports, A and B, are used to connect wired devices on the home network. The Internet port, C, is connected to the modem. The port, labeled D, is the 5V DC power port that supplies power to the router.

Explanation: There are three common methods of signal transmission used in networks:

• Electrical signals – Transmission is achieved by representing data as electrical pulses on copper wire.
• Optical signals – Transmission is achieved by converting the electrical signals into light pulses.
• Wireless signals – Transmission is achieved by using infrared, microwave, or radio waves through the air.

Explanation: Intermediate devices in a network provide network connectivity to end devices and transfer user data packets during data communications.

Explanation: URLs are used to access specific content on a web server through a web browser. The URL identifies the protocol that is being used such as HTTP or FTP, the domain of the server, and the location of the resource on the server.

Explanation: Protocols provide rules that define how a message is transmitted across a network. Implementation requirements such as electronic and bandwidth details for data communication are specified by standards. Operating systems are not specified by protocols, but will implement protocols. Protocols determine how and when to send a message but they do not control the contents of a message.

Explanation: Layer 1 and 2 devices (LAN switch and Ethernet hub) and access point devices do not filter MAC broadcast frames. Only a Layer 3 device, such as a router, can divide a Layer 2 broadcast domain.

Explanation: Because a DHCP client does not have a valid IPv4 address, it must use a broadcast IP address of 255.255.255.255 as the destination address to communicate with the DHCP server. The DHCPDISCOVER message sent by the client is the first message sent in order to make initial contact with a DHCP server.

Explanation: Tethering allows a laptop or PC to use the Internet connection of a mobile device such as a cell phone, usually through a cellular data connection. This allows devices to connect to the Internet in locations where there is no Wi-Fi or cabled connection, but where there is still a cellular data connection.

Explanation: Common media used in networks include copper, glass or plastic optical fiber, and wireless.

Explanation: The IEEE 802.11 standards define Wi-Fi wireless LAN specifications.

Explanation: To help reduce the notation of IPv6 addresses a double colon (::) can replace any single, contiguous string of one or more hextets consisting of all zeros. Only one instance of the double colon can be used in any IPv6 notation.

Explanation: A ping would fail if the destination device was not operational. It would also fail if the DNS server was unavailable to convert the URL to an IP address. The fact that a computer had a static IP address is not a factor. Even if the target protocol (HTTP) is not functioning, the server would still respond to a ping.