CompTIA Updated N10-009 Exam Questions and Answers by emmeline

To verify ownership of a domain, providers commonly require adding a TXT record to DNS containing a specific validation token (a name/value pair). A TXT (text) record is designed to store arbitrary text data associated with a domain or hostname, which makes it ideal for domain verification workflows used by certificate authorities, email security (SPF/DKIM/DMARC-related entries), and third-party services that need proof of administrative control over DNS. This fits Network+ DNS objectives that cover common record types and their practical purposes in real deployments.

An A record maps a hostname to an IPv4 address and is used for name-to-address resolution, not ownership verification. A PTR record provides reverse DNS mapping (IP address to hostname) and is stored in reverse lookup zones, not typically used for validating web domain ownership. A CNAME record creates an alias from one hostname to another canonical hostname; while sometimes used in service integrations, the classic “record name + token value” ownership verification is most directly and universally satisfied by a TXT record. Therefore, TXT is the correct choice given the requirement and the provided record name and value.

DHCP snooping is a security feature on network switches that helps to prevent unauthorized (rogue) DHCP servers from assigning IP addresses to clients. By implementing DHCP snooping, the network administrator can restrict DHCP responses to authorized servers only, preventing unauthorized DHCP configurations, such as incorrect DNS IPs, from being assigned to clients. This helps prevent man-in-the-middle attacks where malicious actors misconfigure DNS to redirect users to fraudulent sites. (Reference: CompTIA Network+ Study Guide, Chapter on Network Security)

Dynamic routing is most beneficial in a growing/changing network because it can automatically learn, adapt, and update routes as the topology changes. In Network+ (N10-009) routing objectives, dynamic routing protocols exchange routing information between routers and recalculate paths when links go down, new networks are added, or metrics change. This reduces the operational burden and the risk of human error that increases as the environment scales. With dynamic routing, adding a new subnet or branch often requires far fewer manual updates because routers propagate new route information automatically, and convergence mechanisms help restore connectivity after failures.

Option A can be partly true in large environments, but the core “best reason” emphasized for dynamic routing is the automatic adaptation to topology changes. Option B is incorrect—dynamic routing may introduce additional security considerations (route filtering, authentication, neighbor control). Option C is not a defining advantage; monitoring visibility depends on tools/telemetry rather than routing type. Therefore, the strongest and most correct reason is automatic changes and updates in network topology.

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For 45 hosts, the minimum subnet size must allow at least 46 usable addresses (1 each for network and broadcast addresses).

A /26 subnet provides 64 addresses, 62 usable — suitable.

A /27 subnet gives only 30 usable — insufficient.

A /25 offers 126 usable — more than needed.

A /28 provides just 14 — too small.

So, the most efficient subnet with minimal wastage is /26.

From Andrew Ramdayal’s guide:

“When designing subnets, always choose the smallest subnet mask that still accommodates all hosts. A /26 provides 62 usable host addresses, suitable for networks with about 50 hosts.”