WGU CompTIA A+ lesson 5 D316 complete questions with expert solutions + rationales

A host is configured with the IP address 172.16.1.100 in the 172.16.1.0/16 IP network. What value should be entered as the subnet mask?

A subnet mask field uses dotted decimal format. The /16 network prefix means that the first 16 bits in the mask are set to one: 11111111 11111111 00000000 00000000. A whole octet of ones converts to 255 in decimal. Therefore, the dotted decimal mask is 255.255.0.0.

What type of value would you expect a query for an AAAA resource record to return?

An IPv6 address.

You are assisting another customer with a full fiber connection terminated to an optical network terminal (ONT). The customer's router was disconnected while some building work was being completed, and the patch cable is now missing. The customer thinks that the cable should be a fiber optic one because the service is "full fiber." What type of cable do you need to locate?

An RJ45 unshielded twisted pair (UTP) patch cable. The ONT converts the optical signal over the external fiber optic cable to an electrical one to connect to the local router.

You are setting up an ADSL router/modem for a client; unfortunately, the contents of the box have become scattered. What type of cable do you need to locate to connect the router's WAN interface?

Asymmetrical Digital Subscriber Line (DSL) connects to the phone line via a filter. You need an RJ11-terminated patch cord to make the connection.

What type of TXT record uses cryptography to help recipient servers reject spoofed messages and spam?

DomainKeys Identified Mail (DKIM)

True or false? A top-level domain such as .com represents the top of the DNS hierarchy.

False. The Domain Name System (DNS) uses root servers at the top of the hierarchy. The root is represented by a trailing dot at the end of a fully qualified domain name (FQDN), though this can very commonly be omitted in ordinary usage.

True or false? A SOHO router uses an embedded modem and Ethernet adapter to forward traffic between public and private network segments over a single hardware port.

False. The modem and Ethernet interfaces use separate ports.

True or false? At the Transport layer, connections between hosts to exchange application data are established over one port number.

False. The server application is identified by one port, but the client must also assign its own port to track the connection.

Another technician has scribbled some notes about a firewall configuration. The technician has listed only the port numbers 25 and 3389. What is the purpose of the protocols that use these ports by default?

Port TCP/25 is used by the Simple Mail Transfer Protocol (SMTP) to send and receive email messages. Port TCP/3389 is used by Remote Desktop Protocol (RDP) to connect to a computer's graphical shell over the network.

The technician has made a note to check that port 445 is blocked by the firewall. What is the purpose of the protocol that uses this port by default, and why should it be blocked?

Port TCP/445 is used by the Server Message Block (SMB) protocol that implements Windows File/Printer Sharing. SMB is designed for use on local networks only. Allowing access from the Internet would be a security risk.

What feature of DHCP means that it must use UDP at the transport layer?

The Dynamic Host Configuration Protocol (DHCP) uses broadcast addressing, which is not supported by the connection-oriented Transmission Control Protocol (TCP). Consequently, DHCP uses the connectionless User Datagram Protocol (UDP).

You are setting up a printer to use static IPv4 addressing. What type of value is expected in the default gateway field?

The IPv4 address of the local router interface, entered in dotted decimal format.

You need to ensure that a print device receives the same IP address when connecting to the network. What value do you need to configure on the DHCP server to enable a reservation?

The reservation should be configured with the media access control (MAC) address of the print device (plus the IP address to assign).

You are advising another technician about typical DNS configuration. The technician thinks that the name server hosting the 515 support domain resource records on the Internet should be configured as the primary DNS server entry in the IP configuration of local clients. Why is this unlikely to be the case?

The role of a name server is to respond to queries for the resource records of the specific domain(s) that it is responsible for. The role of the DNS server types listed in a client's IP configuration is to resolve requests for records in any valid domain. To do this, the resolver must take on the task of querying multiple name servers on behalf of the client. Mixing these roles on the same server machine is possible in theory, but for performance and security reasons, they are more commonly performed by separate servers.

Another technician has scribbled some notes about IPv4 addresses used in various networks associated with support tickets. One of them is assigned to the WAN interface of a SOHO router that requires troubleshooting. Which of these addresses must it be?

52.165.16.254

192.168.100.52

169.254.1.121

172.30.100.32

224.100.100.1

The WAN interface of the router must use an IPv4 address from a valid public range, so 52.165.16.254 is the only one it could be: 172.30.100.32 and 192.168.100.52 are in the class B and class C private ranges, 169.254.1.121 is in the range reserved for APIPA, and 224.100.100.1 is outside the range of valid public addresses (it is part of class D, which is used for a type of addressing called "multicasting").

True or false? A valid IPv6 configuration requires prefix length notation.

True. In IPv6, while there is no separate entity called a subnet mask, as in IPv4, the concept of dividing the address into network and host portions still exists and is necessary. This division is indicated by the prefix length in IPv6, such as /64, /48, etc. The prefix length in IPv6 serves the same purpose as the subnet mask in IPv4, specifying how many bits of the address are allocated for the network portion.

True or false? Both 4G and 5G cellular can be used for fixed access broadband as well as in mobile devices.

True. These can work as an alternative to wired broadband or as a backup/failover Internet connection type. Many router models now come with a cellular radio. A subscribed identity module (SIM) card from the service provider must also be installed.

True or false? A SOHO router can be configured to provide an IPv4 address configuration to hosts without further administrator attention.

True. This service is implemented by the Dynamic Host Configuration Protocol (DHCP).

Which network configuration technology can be configured on switches to divide a local network into multiple broadcast domain segments?

Virtual LAN (VLAN)

Internet Service Providers (ISPs)

Provides Internet connectivity and web services to its customers.

public switched telephone network (PSTN)

Global network connecting national telecommunications systems.

Plain Old Telephone System (POTS)

Parts of a telephone network "local loop" that use voice-grade cabling. Analog data transfer over POTS using dial-up modems is slow (33.3 Kb/s)

Digital Subscriber Line (DSL)

Carrier technology to implement broadband Internet access for subscribers by transferring data over voice-grade telephone lines. There are various "flavors" of DSL, notably S(ymmetric)DSL, A(symmetric)DSL, and V(ery HIgh Bit Rate)DSL.

Fixed wireless Internet access

A method for accessing the internet in areas where wired broadband is unavailable. It includes satellite-based systems, such as Geostationary Orbital Satellite Internet, which offers broad coverage with typical speeds of 2-6 Mbps up and 30 Mbps down but higher latency (600-800 ms RTT), and Low Earth Orbital Satellite Internet, which offers better bandwidth (70-100 Mbps) and lower latency (100-200 ms RTT) but requires a motorized, phased array antenna to track the moving satellites.

Fiber to the Premises (FTTP)

Internet connection type that uses a fiber link between the subscriber premises and ISP network. Fiber to the premises (FTTP) uses a full fiber link, while fiber to the curb (FTTC) retains a short segment of copper wire between the subscriber premises and a street cabinet.

optical network terminal (ONT)

Device that converts between optical and electrical signaling deployed to facilitate full fiber Internet connection types.

Satellite

System of microwave transmissions where orbital satellites relay signals between terrestrial receivers or other orbital satellites. Satellite internet connectivity is enabled through a reception antenna connected to the PC or network through a DVB-S modem.

Wireless Internet Service Provider (WISP)

ISP offering Internet access over ground-based Line of Sight (LoS) microwave transmitters.

Cellular radio

Standards for implementing data access over cellular networks are implemented as successive generations. For 2G (up to about 48 Kb/s) and 3G (up to about 42 Mb/s), there are competing GSM and CDMA provider networks. Standards for 4G (up to about 90 Mb/s) and 5G (up to about 300 Mb/s) are developed under converged LTE standards.

Global System for Mobile Communication (GSM)

Standard for cellular radio communications and data transfer. GSM phones use a SIM card to identify the subscriber and network provider. 4G and later data standards are developed for GSM.

Code Division Multiple Access (CDMA)

Method of multiplexing a communications channel using a code to key the modulation of a particular signal. CDMA is associated with Sprint and Verizon cellular phone networks.

Router

Intermediate system working at the Network layer capable of forwarding packets around logical networks of different layer 1 and layer 2 types.

Firewall

Software or hardware device that protects a network segment or individual host by filtering packets to an access control list.

Transmission Control Protocol/Internet Protocol (TCP/IP)

Network protocol suite used to implement the Internet and most WANs and LANs. It uses a four-layer network model that corresponds roughly to the OSI model as follows: Network Interface (Physical/Data Link), Internet (Network), Transport (Transport), Application (Session, Presentation, Application).

Transmission Control Protocol (TCP)

Protocol in the TCP/IP suite operating at the transport layer to provide connection-oriented, guaranteed delivery of packets.

User Datagram Protocol (UDP)

Protocol in the TCP/IP suite operating at the transport layer to provide connectionless, non-guaranteed communication.

Internet Protocol (IP)

Network (Internet) layer protocol in the TCP/IP suite providing packet addressing and routing for all higher-level protocols in the suite.

IPv4

Version of the Internet Protocol that uses 32-bit address values and subnet masks typically expressed in dotted decimal notation.

Subnet mask

Number of bits applied to an IP address to mask the network ID portion from the host/interface ID portion.

Default gateway

IP configuration parameter that identifies the address of a router on the local subnet that the host can use to contact other networks.

Public IP address

Some IP address ranges are designated for use on private networks only. Packets with source IP addresses in public ranges are permitted to be forwarded over the Internet. Packets with source IP addresses from private ranges should be blocked at Internet gateways or forwarded using some type of translation mechanism.

Network Address Translation (NAT)

Routing mechanism that conceals internal addressing schemes from the public Internet by translating between a single public address on the external side of a router and private, non-routable addresses internally.

Domain Name System (DNS)

Service that maps fully qualified domain name labels to IP addresses on most TCP/IP networks, including the Internet.

Dynamic Host Configuration Protocol (DHCP)

Protocol used to automatically assign IP addressing information to hosts that have not been configured manually.

Automatic private IP addressing (APIPA)

Mechanism for Windows hosts configured to obtain an address automatically that cannot contact a DHCP server to revert to using an address from the range 169.254.x.y. This is also called a link-local address.

IPv6

Version of the Internet Protocol that uses 128-bit address values typically expressed in canonical hex notation with slash notation network prefixes.

Hypertext Transfer Protocol (HTTP)/HyperText Transfer Protocol Secure (HTTPS)

Application protocol used to provide web content to browsers. HTTP uses port 80. HTTPS(ecure) provides for encrypted transfers, using TLS and port 443.

Secure Shell (SSH)

Application protocol supporting secure tunneling and remote terminal emulation and file copy. SSH runs over TCP port 22.

Describe the Trivial File Transfer Protocol (TFTP)

The Trivial File Transfer Protocol (TFTP) is a simplified form of the File Transfer Protocol (FTP) and supports only file copying. TFTP works over UDP port 69, whereas FTP work on port 21.

Scope

Range of consecutive IP addresses in the same subnet that a DHCP server can lease to clients.

Lease

Address configuration assigned by a DHCP server to a client for a limited period.

Reserve

DHCP configuration that assigns either a prereserved or persistent IP address to a given host, based on its hardware address or other ID.

Host name

A human-readable name that identifies a network host.

Fully Qualified Domain Name (FQDN)

Unique label specified in a DNS hierarchy to identify a particular host within a subdomain within a top-level domain.

Resource records

Data file storing information about a DNS zone. The main records are as follows: A (maps a host name to an IPv4 address), AAAA (maps to an IPv6 address), CNAME (an alias for a host name), MX (the IP address of a mail server), and PTR (allows a host name to be identified from an IP address).

MX record

Type of DNS resource record used to identify the email servers used by a domain.

TXT record

DNS resource record for storing free-form string values.

Spam

Junk, fraudulent, and malicious messaging sent over email (or instant messaging, which is called spam). Spam can also be spread via social networking.

Sender Policy Framework (SPF)

DNS record identifying hosts authorized to send mail for the domain.

DomainKeys Identified Mail (DKIM)

Cryptographic authentication mechanism for mail utilizing a public key published as a DNS record.

Domain-Based Message Authentication, Reporting, and Conformance (DMARC)

Framework for ensuring proper application of SPF and DKIM utilizing a policy published as a DNS record.

Virtual LAN (VLAN)

Logical network segment comprising a broadcast domain established using a feature of managed switches to assign each port a VLAN ID. Even though hosts on two VLANs may be physically connected to the same switch, local traffic is isolated to each VLAN, so they must use a router to communicate.

Virtual Private Network (VPN)

Secure tunnel created between two endpoints connected via an unsecure transport network (typically the Internet).