CompTIA Network+ (N10-009) practice questions

A network designer needs each subnet to provide exactly six usable host addresses, with no addresses wasted beyond the network and broadcast addresses. Which IPv4 prefix length meets this requirement?

• A/29check_circle Correct
• B/27
• C/28
• D/30

Why A is correct: A /29 leaves three host bits, so two to the third power is eight addresses, and subtracting the network and broadcast addresses leaves exactly six usable hosts.

Why B is wrong: A /27 leaves five host bits, giving 32 addresses and 30 usable hosts; tempting if you stop at the host-bit field, but it is far larger than six.

Why C is wrong: A /28 leaves four host bits, giving 16 addresses and 14 usable hosts; tempting if you miscount by a single host bit, but it doubles the size needed.

Why D is wrong: A /30 leaves two host bits, giving four addresses and two usable hosts, the point-to-point size; tempting but it supplies only two hosts, not six.

On a single access switch, PC-A sits in VLAN 10 (subnet 10.1.10.0/24) and PC-B sits in VLAN 20 (subnet 10.1.20.0/24). Both link lights are up and each PC reaches other hosts inside its own VLAN, but PC-A cannot ping PC-B. What is required to let the two PCs communicate while keeping the VLANs separate?

• AEnable an 802.1Q trunk between the two switchports so the VLAN tags carry the traffic across.
• BAdd a Layer 3 device such as a router or multilayer switch to route between the VLAN 10 and VLAN 20 subnets.check_circle Correct
• CEnable Spanning Tree Protocol for VLAN 10 and VLAN 20 to open a forwarding path between them.
• DConfigure port security on both switchports to permit each PC's MAC address.

Why A is wrong: Trunking sounds like it connects VLANs, but an 802.1Q trunk multiplexes several VLANs onto one switch-to-switch link; it does not route packets from one VLAN subnet into another.

Why B is correct: Each VLAN is a separate broadcast domain on its own IP subnet, so traffic between them must cross a Layer 3 boundary provided by a router subinterface or a multilayer switch SVI.

Why C is wrong: STP is tempting because it manages forwarding paths, but it only prevents Layer 2 loops within a broadcast domain and never routes traffic between two different VLAN subnets.

Why D is wrong: Port security is tempting when a host cannot pass traffic, but it only limits which MAC addresses a port accepts and does nothing to forward traffic between two separate VLAN subnets.

A technician captures traffic on a switch mirror port and finds that user login credentials for an internal web application are travelling in readable cleartext over HTTP, so anyone with packet-capture access can read them. Which element of the CIA triad is most directly compromised by this finding?

• AIntegrity, because an attacker who reads the credentials could later modify the account, so the trustworthiness of the stored data is the main loss.
• BAvailability, because exposing the login could lead to the account being locked out and the legitimate user then denied access to the application.
• CConfidentiality, because the credentials can be read by an unauthorised party who captures the packets, defeating the aim of keeping data secret in transit.check_circle Correct
• DNon-repudiation, because cleartext credentials would make it impossible to prove who carried out a given action later on.

Why A is wrong: Integrity concerns unauthorised alteration of data; capturing readable credentials exposes them but does not change any stored value, so this is not the principle harmed here.

Why B is wrong: Availability is about authorised users reaching a service; the web application stays reachable and no disruption has occurred, so availability is not what the cleartext exposure breaks.

Why C is correct: Confidentiality is the assurance that data is disclosed to authorised parties alone; cleartext credentials on the wire can be read by anyone capturing packets, which is precisely this loss.

Why D is wrong: Non-repudiation is the inability to deny an action and is not one of the three CIA-triad pillars, so it cannot be the triad element compromised by packet exposure.