CompTIA Network+ — All Questions

Host 10.1.5.130 with a /25 mask belongs to which subnet network address?

• a.10.1.5.128✓
• b.10.1.5.0
• c.10.1.5.64
• d.10.1.5.96

A /25 splits the last octet into blocks of 128, producing subnets .0 and .128. The host .130 falls in the second block, so its network address is 10.1.5.128. The broadcast for that subnet would be 10.1.5.255.

A /30 subnet, commonly used for point-to-point router links, provides how many usable host addresses?

• a.6
• b.1
• c.4
• d.2✓

A /30 leaves 2 host bits, giving 4 total addresses minus the network and broadcast, for 2 usable hosts. That is exactly enough for the two ends of a point-to-point link. This efficiency is why /30 is traditional for router interconnections.

How many /27 subnets can be created from a single /24 network?

• a.16
• b.4
• c.32
• d.8✓

Moving from /24 to /27 borrows 3 host bits, and 2 to the 3rd power equals 8 subnets. Each /27 provides 30 usable hosts. The formula 2 to the number of borrowed bits gives the subnet count.

What is the broadcast address of the network 172.16.4.0/22?

• a.172.16.255.255
• b.172.16.7.255✓
• c.172.16.4.255
• d.172.16.4.63

A /22 mask is 255.255.252.0, giving a block size of 4 in the third octet, so 172.16.4.0 spans 172.16.4.0 through 172.16.7.255. The broadcast address is therefore 172.16.7.255. The last usable host is 172.16.7.254.

An IPv6 address is composed of how many bits?

• a.256
• b.128✓
• c.64
• d.32

IPv6 uses 128-bit addresses, written as eight groups of four hexadecimal digits. This vastly expands the address space compared with IPv4's 32 bits. The larger space removes the practical scarcity that drove IPv4 NAT adoption.

Which IPv6 prefix is reserved for unique local addresses, the rough equivalent of IPv4 RFC 1918 private space?

• a.FF00::/8
• b.FC00::/7✓
• c.2000::/3
• d.FE80::/10

Unique local addresses use the FC00::/7 range (in practice FD00::/8) and are routable within an organization but not on the public internet. FE80::/10 is link-local, FF00::/8 is multicast, and 2000::/3 is global unicast. ULAs provide private-style addressing for IPv6.

Which IPv6 address is the loopback used to test the local protocol stack?

• a.FF02::1
• b.FE80::1
• c.::
• d.::1✓

The IPv6 loopback address is ::1, the equivalent of 127.0.0.1 in IPv4, used to test the local TCP/IP stack. The all-zeros :: is the unspecified address. FF02::1 is the all-nodes multicast address on the local link.

Which IPv6 mechanism lets a host automatically generate its own global address from a router-advertised prefix without a DHCP server?

• a.APIPA
• b.SLAAC✓
• c.NAT66
• d.DHCPv6 stateful

Stateless Address Autoconfiguration (SLAAC) lets a host build its own address by combining the prefix from a Router Advertisement with a locally generated interface identifier. No DHCP server is required. APIPA is an IPv4 concept, and stateful DHCPv6 does track assignments centrally.

Which process forms the 64-bit IPv6 interface identifier from a 48-bit MAC address by inserting FFFE and flipping a bit?

• a.Stateful DHCPv6
• b.Anycast assignment
• c.EUI-64✓
• d.SLAAC prefix delegation

EUI-64 expands a 48-bit MAC into a 64-bit interface identifier by inserting FFFE in the middle and flipping the seventh bit of the first byte. SLAAC often uses EUI-64 to build the host portion of an address. Privacy extensions can replace it with randomized identifiers.

Which address range does a Windows host self-assign when it cannot reach a DHCP server?

• a.172.16.0.0/12
• b.192.168.0.0/16
• c.169.254.0.0/16✓
• d.10.0.0.0/8

APIPA self-assigns an address from 169.254.0.0/16 when no DHCP server responds, allowing local-link communication only. The other ranges are RFC 1918 private blocks that are normally assigned deliberately. Seeing a 169.254 address is a strong sign of a DHCP problem.

Which transition approach runs IPv4 and IPv6 simultaneously on the same interfaces so hosts can use either protocol?

• a.6to4 only
• b.Dual stack✓
• c.Tunneling
• d.NAT64

Dual stack configures both IPv4 and IPv6 on the same interfaces so a host can communicate over whichever protocol a destination supports. It is the most straightforward migration method. Tunneling and NAT64 address cases where only one protocol is available end to end.

Under legacy classful addressing, what is the default subnet mask for a Class B network?

• a.255.255.0.0✓
• b.255.255.255.0
• c.255.255.255.128
• d.255.0.0.0

Class B networks span 128.0.0.0 through 191.255.255.255 and use a default mask of 255.255.0.0, or /16. Class A defaults to 255.0.0.0 and Class C to 255.255.255.0. Modern networks use CIDR rather than rigid classful boundaries.

Which IPv4 address range is reserved for multicast group traffic?

• a.10.0.0.0/8
• b.127.0.0.0/8
• c.224.0.0.0/4✓
• d.169.254.0.0/16

The 224.0.0.0/4 range (224.0.0.0 through 239.255.255.255), historically Class D, is reserved for multicast. Multicast delivers a single stream to many subscribed receivers efficiently. The other ranges are loopback, APIPA, and private unicast respectively.

Which TCP port does FTP use for its control connection carrying commands and responses?

• a.21✓
• b.22
• c.69
• d.20

FTP uses TCP port 21 for the control channel that carries commands and server responses, while port 20 handles active-mode data transfer. Port 22 is SSH and port 69 is TFTP. Separating control and data is a defining trait of FTP.

Which well-known TCP port is used by SMTP to relay email between mail servers?

• a.993
• b.110
• c.143
• d.25✓

SMTP uses TCP port 25 to transfer email between servers. Ports 110 and 143 are POP3 and IMAP for retrieval, and 993 is secure IMAP. Submission from clients often uses port 587 with authentication.

Which TCP port does IMAP use by default to retrieve and synchronize email from a server?

• a.25
• b.110
• c.389
• d.143✓

IMAP uses TCP port 143 and, unlike POP3, keeps messages on the server and synchronizes folder state across devices. POP3 on port 110 typically downloads and deletes mail. Secure IMAP over TLS uses port 993.

On which UDP port does an SNMP agent listen for polling requests from a management station?

• a.514
• b.161✓
• c.123
• d.162

SNMP agents listen on UDP port 161 for get and set requests, while traps are sent to the manager on UDP 162. Port 514 is syslog and 123 is NTP. Knowing this pair is key to allowing monitoring through firewalls.

Which TCP port is used by Microsoft's Remote Desktop Protocol for graphical remote sessions?

• a.5900
• b.22
• c.23
• d.3389✓

RDP uses TCP port 3389 to provide graphical remote access to Windows systems. Port 5900 is VNC, port 22 is SSH, and 23 is Telnet. Exposing 3389 directly to the internet is a common security risk.

Which TCP or UDP port does LDAP use for unencrypted directory queries?

• a.636
• b.445
• c.389✓
• d.88

LDAP uses port 389 for standard, unencrypted directory lookups. The secure variant LDAPS uses port 636. Port 88 is Kerberos and 445 is SMB, both common in the same directory environments.

Which TCP port does modern SMB use for Windows file and printer sharing over TCP/IP?

• a.139
• b.137
• c.3389
• d.445✓

Modern SMB (CIFS) runs directly over TCP port 445 for file and printer sharing. Legacy NetBIOS used ports 137 through 139. Port 445 is frequently targeted by worms, so it should be filtered at the perimeter.

Which UDP port do network devices commonly use to send syslog messages to a logging server?

• a.514✓
• b.123
• c.161
• d.69

Syslog traditionally uses UDP port 514 to forward event messages to a central log server. SNMP uses 161, NTP uses 123, and TFTP uses 69. Reliable variants can carry syslog over TCP, sometimes with TLS.

Which TCP port does the insecure, clear-text Telnet remote-terminal protocol use?

• a.23✓
• b.25
• c.22
• d.21

Telnet uses TCP port 23 and transmits everything, including credentials, in clear text. SSH on port 22 is the secure replacement. Telnet should be disabled on production devices for security reasons.

Which UDP port does TFTP use, often for network device firmware and configuration transfers?

• a.161
• b.69✓
• c.20
• d.21

TFTP uses UDP port 69 and is a lightweight, unauthenticated file-transfer protocol often used to load firmware or configs onto network devices. It lacks the reliability and security of FTP. Its simplicity makes it convenient on the LAN but unsafe across untrusted links.

Which TCP port carries LDAP directory traffic secured with SSL or TLS as LDAPS?

• a.989
• b.636✓
• c.389
• d.443

LDAPS encrypts directory traffic and uses TCP port 636. Standard LDAP on 389 is unencrypted. Port 443 is HTTPS and 989 is FTPS data, so neither applies to secure directory queries.

Which port is used by unencrypted SIP for setting up and tearing down VoIP calls?

• a.5060✓
• b.5061
• c.1720
• d.554

SIP signaling for VoIP call setup and teardown uses port 5060 without encryption, while 5061 is used for SIP over TLS. Port 1720 is H.323 and 554 is RTSP for streaming. SIP handles signaling while RTP carries the actual media.

Which TCP port does POP3 use to download email, typically removing it from the server?

• a.143
• b.110✓
• c.465
• d.25

POP3 uses TCP port 110 and generally downloads messages to a single device, removing them from the server. IMAP on 143 keeps mail synchronized on the server. Secure POP3 over TLS uses port 995.

Which port does Kerberos use for authentication in Windows Active Directory environments?

• a.636
• b.88✓
• c.445
• d.389

Kerberos authentication uses port 88 to issue and validate tickets in Active Directory. LDAP uses 389, LDAPS 636, and SMB 445 in the same environments. Kerberos provides single sign-on through its ticket-granting mechanism.

Which TCP port carries unencrypted HTTP web traffic by default?

• a.21
• b.80✓
• c.8080
• d.443

HTTP uses TCP port 80 for unencrypted web traffic. Port 443 carries HTTPS with TLS encryption, and 8080 is a common alternate proxy or web port. Modern sites redirect port 80 to 443 for security.

Which default TCP port does Microsoft SQL Server listen on for database client connections?

• a.3306
• b.1521
• c.1433✓
• d.5432

Microsoft SQL Server listens on TCP port 1433 by default. MySQL uses 3306, Oracle 1521, and PostgreSQL 5432. Database ports should be restricted to application servers rather than exposed broadly.

Which sequence correctly lists the four DHCP messages a client and server exchange to obtain a lease?

• a.Offer, Discover, Acknowledge, Request
• b.Discover, Request, Offer, Acknowledge
• c.Discover, Offer, Request, Acknowledge✓
• d.Request, Offer, Discover, Acknowledge

The DHCP process follows the DORA sequence: the client broadcasts a Discover, the server sends an Offer, the client sends a Request for the offered address, and the server confirms with an Acknowledge. Remembering DORA keeps the order straight. Only after the ACK does the client use the leased address.

Which DNS record type maps a hostname to an IPv4 address?

• a.CNAME
• b.MX
• c.AAAA
• d.A✓

The A record maps a hostname to a 32-bit IPv4 address. The AAAA record does the same for IPv6, MX points to mail servers, and CNAME creates an alias. A records are the most common forward-lookup entries.

Which DNS record type resolves a hostname to an IPv6 address?

• a.PTR (reverse pointer)
• b.TXT
• c.A
• d.AAAA✓

The AAAA (quad-A) record maps a hostname to a 128-bit IPv6 address. The A record handles IPv4, PTR handles reverse lookups, and TXT holds arbitrary text. Dual-stack hosts commonly have both A and AAAA records.

Which DNS record identifies the mail server responsible for accepting email for a domain?

• a.CNAME
• b.MX✓
• c.SRV
• d.NS

The MX (Mail Exchange) record specifies the mail servers that accept email for a domain, along with a priority value. Lower priority numbers are preferred. SRV records locate other services, while NS records delegate the zone.

Which DNS record creates an alias that points one hostname to another canonical name?

• a.CNAME✓
• b.PTR
• c.SOA
• d.A

A CNAME (Canonical Name) record aliases one hostname to another, so www can point to a canonical host that itself has an A record. It avoids duplicating address records. A CNAME should not coexist with other record types for the same name.

Which DNS record maps an IP address back to a hostname for reverse lookups?

• a.TXT
• b.A
• c.PTR✓
• d.MX

The PTR (pointer) record provides reverse DNS, mapping an IP address to a hostname within the in-addr.arpa or ip6.arpa zones. Mail servers often check PTR records to help verify sender legitimacy. It is the inverse of an A or AAAA record.

Which DNS record type holds free-form text and is used for SPF, DKIM, and domain-verification data?

• a.SRV
• b.CNAME
• c.TXT✓
• d.NS

The TXT record stores arbitrary text and is widely used for email authentication such as SPF and DKIM, plus domain ownership verification. It carries policy data rather than addressing. Its flexibility makes it central to modern email security.

In a DNS record, what does the TTL value control?

• a.How long a resolver may cache the record✓
• b.The priority of a mail server
• c.The UDP port the query is sent to
• d.The maximum size of the DNS response packet

The DNS TTL tells resolvers how many seconds they may cache a record before querying again for a fresh copy. Lower TTLs speed propagation of changes but increase query load. Administrators lower TTLs before planned changes to reduce stale answers.

Which term describes a DNS resolver that takes full responsibility for querying other servers and returning a final answer to the client?

• a.Root hint server
• b.Authoritative-only server
• c.Iterative forwarder
• d.Recursive resolver✓

A recursive resolver accepts a client's query and does the work of contacting root, TLD, and authoritative servers until it has the final answer. The client makes one request and gets one answer. Authoritative servers, by contrast, only answer for the zones they host.

In NTP, what does the stratum number indicate?

• a.The distance in hops from a reference clock✓
• b.The encryption strength of the time source
• c.The UDP port used for synchronization
• d.The number of clients a server can serve

The NTP stratum indicates how many steps a time source is from an authoritative reference clock, with stratum 0 being the reference itself and stratum 1 directly attached. Higher stratum numbers are further away and slightly less accurate. Clients typically sync to low-stratum servers.

Which DHCP feature guarantees that a specific device always receives the same IP address based on its MAC address?

• a.Exclusion range
• b.Lease time
• c.Scope option
• d.Reservation✓

A DHCP reservation ties a specific MAC address to a fixed IP so the device always gets the same address while still using DHCP. Exclusions merely remove addresses from the pool, and scope options set parameters like DNS. Reservations suit printers and servers that need consistent addressing.

On which UDP port does NTP exchange time-synchronization messages?

• a.53
• b.67
• c.514
• d.123✓

NTP uses UDP port 123 to synchronize clocks between devices and time sources. Port 53 is DNS, 67 is DHCP, and 514 is syslog. Accurate time from NTP underpins logging, certificates, and authentication.

Which UDP port pair does DHCP use for server and client communication?

• a.80 and 8080
• b.53 and 54
• c.67 and 68✓
• d.137 and 138

DHCP servers listen on UDP port 67 and clients receive on UDP port 68. These ports are essential to allow through firewalls or configure in DHCP relays. Knowing them helps diagnose why clients fail to obtain addresses.

Which DNS record identifies the authoritative name servers for a zone?

• a.MX
• b.PTR
• c.NS✓
• d.A

NS (Name Server) records list the authoritative name servers for a zone and are used to delegate subdomains. MX points to mail servers, PTR handles reverse lookups, and A maps names to IPv4 addresses. Correct NS records are essential for delegation to work.

A company uses a web-based email and CRM suite that the provider fully manages, with no OS or application maintenance by the customer. Which cloud model is this?

• a.PaaS
• b.DaaS
• c.IaaS
• d.SaaS✓

Software as a Service (SaaS) delivers complete, provider-managed applications accessed over the web, with the customer managing only data and users. IaaS and PaaS require the customer to manage more of the stack. Email and CRM suites are classic SaaS examples.

Which cloud service model gives developers a managed platform of runtime, OS, and middleware to deploy their own applications without managing servers?

• a.On-premises
• b.PaaS✓
• c.IaaS
• d.SaaS

Platform as a Service (PaaS) provides a managed environment, including the operating system, runtime, and middleware, so developers deploy code without maintaining the underlying infrastructure. IaaS gives raw compute the customer must manage, and SaaS gives finished apps. PaaS accelerates development.

An organization keeps sensitive workloads in its private data center but bursts to a public provider during peak demand. Which cloud deployment model is this?

• a.Private cloud
• b.Public cloud
• c.Community cloud
• d.Hybrid cloud✓

A hybrid cloud combines private infrastructure with public cloud resources, allowing sensitive workloads to stay private while bursting to public capacity when needed. This balances control with scalability. Cloud bursting is a common hybrid use case.

Which cloud characteristic allows resources to automatically expand and contract in response to changing demand?

• a.Elasticity✓
• b.Multitenancy
• c.Metered billing
• d.Broad network access

Elasticity lets cloud resources scale up during spikes and scale down when demand falls, often automatically. This ensures performance during peaks while avoiding paying for idle capacity. It is a defining advantage of cloud over fixed on-premises hardware.

Which cloud construct provides a logically isolated, customer-defined virtual network with its own subnets and routing inside a public provider?

• a.Network function virtualization (NFV)
• b.Availability zone
• c.Virtual private cloud (VPC)✓
• d.Content delivery network (CDN)

A Virtual Private Cloud (VPC) is a logically isolated section of a public cloud where a customer defines subnets, route tables, and gateways. It gives control similar to an on-premises network within the provider. CDNs cache content, and availability zones describe physical data-center groupings.