CompTIA Network+Free IT Professional Network Knowledge practice test

Correct answer: B. MIMO

Multiple Input, Multiple Output (MIMO) leverages several transmit and receive antennas at the same time, dramatically raising the data rate available to 802.11n radios. CSMA/CA is the media-access scheme used on Wi-Fi to keep stations from transmitting simultaneously, but it doesn't increase throughput. CSMA/CD is the equivalent collision-handling method on legacy wired Ethernet. MIRO is a made-up acronym and is not a real wireless technology.

Correct answer: C. IGMP

Internet Group Management Protocol (IGMP) is the standard hosts use to signal to their local router that they wish to join or leave an IP multicast group, which is exactly the function described. Protocol Independent Multicast Sparse Mode (PIM-SM) and Protocol Independent Multicast Dense Mode (PIM-DM) are router-to-router protocols used to build distribution trees and forward multicast traffic between routers; neither performs host group registration. Shortest Path Tree (SPT) is a forwarding tree concept used in multicast routing rather than a host-membership protocol.

Correct answer: C. 100 Mbps

Even though far quicker variants like Gigabit and 10-Gigabit Ethernet now exist, the nickname "Fast Ethernet" still refers to the 100 Mbps family, originally branded as 100BaseT and including 100BaseTX, 100BaseT4, and 100BaseT2. 10 Mbps describes 10BaseT, an older Ethernet generation. The 1 Gbps tier is generally called Gigabit Ethernet (1000BaseTX, 1000BaseSX, 1000BaseCX, 1000BaseLX), and 10 Gbps Ethernet uses 802.3 variants such as 10GBaseT, 10GBaseSR, and 10GBaseLR.

Correct answer: B. Connecting two switches together

Crossover cables are the right pick whenever two devices of the same type (or two devices that traditionally use the same wiring scheme) need to talk to each other. Common cases include switch-to-switch, hub-to-hub, hub-to-switch, host-to-host, and router-direct-to-host. A straight-through cable is what you want for the other listed connections: host-to-switch, host-to-hub, and router-to-switch.

Correct answer: C. Explicit deny

A rule that the administrator has written specifically to drop or block traffic to a given port or protocol is an explicit deny. Firewalls are commonly configured one of two ways: a default-allow stance (implicit permit) where the administrator adds explicit denies to block exceptions, or a default-block stance (implicit deny) where the administrator adds explicit permits for traffic that should pass. An explicit permit is a hand-written rule that lets traffic through. An implicit permit means traffic is allowed when no rule matches. An implicit deny means traffic is blocked when no rule matches.

Correct answer: C. Router

A /25 prefix produces two equal-sized subnets: 172.16.40.0–172.16.40.127 (network 172.16.40.0, broadcast 172.16.40.127) and 172.16.40.128–172.16.40.255 (network 172.16.40.128, broadcast 172.16.40.255). The address 172.16.40.70 falls in the first range and 172.16.40.190 falls in the second, so the two hosts live on different IP networks. Anytime traffic must move between IP subnets, a routing function is required, so a router is the answer. A Layer 2 switch only forwards within a single broadcast/IP domain using MAC addresses and never makes routing decisions. A firewall enforces security policy on traffic but is not what bridges separate IP subnets. A hub is a Layer 1 repeater that mirrors bits to all ports without any logic at all.

Correct answer: C. Multiport repeater

A hub has no intelligence of its own. Whatever signal arrives on one port is regenerated and pushed back out every other port, making it essentially a repeater with many ports — hence the term multiport repeater. Because it merely re-emits the bit stream, it lives at the physical layer and interacts directly with the cabling. A Layer 2 switch operates at the data link layer and gives every port its own collision domain, which a hub cannot do. A router is a Layer 3 device that forwards packets based on IP, performing a very different function. A transparent bridge, like a switch, also segments collision domains rather than mindlessly mirroring traffic.

Correct answer: C. Configuring quality of service

Quality of Service (QoS) lets administrators classify and prioritize specific traffic flows. Real-time media such as voice and videoconferencing can be tagged for low-latency forwarding ahead of less-sensitive traffic like web browsing or social-media downloads, smoothing out the choppiness users are experiencing. Acceptable use policies are administrative controls and don't influence packet scheduling. Content caching positions copies of static data nearer to users — useful for retrieval performance, but not relevant to interactive media stutter. Hardware redundancy improves availability but doesn't address congestion or prioritization.

Correct answer: D. SMTP

Simple Mail Transfer Protocol (SMTP) traditionally listens on TCP port 25 and is the protocol clients and mail servers use to push outbound email. Allowing TCP/25 therefore opens an SMTP path through the firewall. File Transfer Protocol (FTP) uses TCP ports 20 and 21. Secure Shell (SSH) listens on TCP/22. HTTPS rides on TCP/443.

Correct answer: A. 20 and 21

FTP runs strictly over TCP and uses two well-known ports: 21 for the control channel (commands) and 20 for the data channel in active mode. FTP transfers data unencrypted, so it should be replaced with a secure alternative whenever possible. SFTP wraps file transfer inside the SSH session on TCP/22 and provides encryption. HTTP only uses a single port (80, not 81) and is an application-layer web protocol. Telnet, on TCP/23, is a deprecated cleartext remote-login protocol that has largely been superseded by SSH.