Chapter 11: Networking Fundamentals and Devices (Set-10)
When two PCs on the same switch cannot communicate, but both can ping the gateway, the most likely issue is
A Wrong SSID name
B Weak fiber signal
C Different VLANs
D Low monitor size
If both PCs can reach the gateway, Layer-3 connectivity exists. If they can’t reach each other, they may be placed in different VLANs. VLAN separation blocks Layer-2 communication unless routing rules allow it.
A switch can forward frames correctly only after learning a device’s MAC from the
A Destination IP field
B Subnet mask field
C DNS name field
D Source MAC field
Switches learn MAC addresses by reading the source MAC of incoming frames and mapping it to the incoming port. This MAC table allows efficient forwarding to the correct destination port.
In a network loop, broadcast frames can multiply endlessly, creating a
A DNS failure
B Broadcast storm
C NAT timeout
D IP shortage
A loop can make broadcast frames circulate and grow rapidly, consuming bandwidth and CPU. This leads to extreme slowness or network outage. Proper design and loop prevention features avoid storms.
If throughput is far below bandwidth on a Wi-Fi link, a likely technical reason is
A SSID too short
B MAC too long
C Retransmissions high
D DNS too fast
Wireless interference and weak signals cause packet errors. Wi-Fi then retransmits frames, reducing effective throughput. Even with high link rate, repeated retransmissions lower actual user speed.
A trunk link is required between switches when you must carry
A Multiple VLANs
B Multiple printers
C Multiple monitors
D Multiple keyboards
Trunk ports carry traffic for many VLANs using VLAN tags. This allows the same VLANs to exist across different switches while keeping each VLAN’s traffic logically separated.
Inter-VLAN communication normally requires
A Hub broadcasting
B Repeater boosting
C Coax shielding
D Routing function
VLANs are separate Layer-2 networks. Devices in different VLANs need a router or Layer-3 switch to route packets between VLANs. Without routing, VLANs remain isolated.
A device getting 169.254.x.x indicates the device
A Used public IP
B Enabled WPA3
C Missed DHCP lease
D Disabled NAT
169.254.x.x is an APIPA address assigned when DHCP fails. The device did not receive IP settings from DHCP, so internet access usually fails until DHCP or connectivity is restored.
A wrong default gateway typically results in
A No external access
B Faster LAN speed
C Better Wi-Fi signal
D More MAC learning
With a wrong gateway, the device can often talk locally but cannot reach outside networks like the internet. External traffic is sent to the wrong router address and fails to route properly.
If ping to an IP works but website names fail, the primary suspect is
A Cable quality
B VLAN trunk
C Router NAT
D DNS settings
Connectivity to an IP proves routing works. Name resolution failing indicates DNS issues, such as wrong DNS server address or DNS server unavailability. Correct DNS settings restore normal browsing.
In classic bus networks, terminators are used to prevent
A VLAN overlap
B IP conflict
C Signal reflection
D MAC spoofing
Terminators absorb signals at the bus cable ends. Without them, reflections cause noise and errors. Proper termination is essential for reliable transmission in older coax-based bus topology networks.
A hub creates a single shared
A VLAN domain
B Collision domain
C DNS domain
D Routing domain
Hubs repeat data to all ports, so all devices compete on the same medium. Collisions can occur when multiple devices transmit at once, reducing speed and efficiency compared to switches.
A switch reduces collisions because each port becomes a
A Shared collision domain
B Shared broadcast domain
C Separate collision domain
D Separate DNS domain
Switch ports isolate collision domains, allowing multiple devices to transmit simultaneously without collisions across ports. This improves performance compared to hubs, especially when many devices are active.
A router separates broadcast domains because it does not
A Learn MACs
B Use switches
C Use DNS
D Forward broadcasts
Routers usually block Layer-2 broadcasts from passing between interfaces. This divides networks into separate broadcast domains, reducing broadcast traffic spread and improving network stability and security.
NAT is essential in many IPv4 home networks because it allows
A Many VLAN tags
B Many private users
C Many MAC tables
D Many DNS caches
NAT translates many private IP addresses to one public IP. This enables multiple devices to share a single ISP connection and reduces demand for public IPv4 addresses.
MAC filtering is weak security because attackers can
A Spoof subnet mask
B Spoof SSID length
C Spoof MAC address
D Spoof bandwidth value
MAC addresses can be captured and imitated. An attacker can set their device’s MAC to an allowed one. Therefore, MAC filtering should not replace WPA2/WPA3 encryption and strong passwords.
WPA3 improves Wi-Fi security mainly by providing
A Stronger authentication
B Longer SSID names
C Faster NAT speed
D Wider coax cables
WPA3 uses improved security methods that make password guessing harder and strengthens encryption. It offers better protection than WPA2, especially against certain offline attacks.
Disabling WPS is recommended mainly to reduce risk of
A DNS poisoning
B VLAN leakage
C Fiber bending
D PIN brute force
WPS PIN methods can be attacked by repeated guesses. If successful, attackers can join the Wi-Fi network. Disabling WPS and using WPA2/WPA3 with strong passwords is safer.
A proxy server is commonly deployed to
A Assign MAC address
B Boost Wi-Fi range
C Filter web access
D Replace gateway
A proxy can enforce browsing policies, log usage, and sometimes cache content. Organizations use proxies to control internet access, improve security, and manage bandwidth usage.
Load balancing increases availability because it can
A Redirect on failure
B Increase IP conflicts
C Disable encryption
D Slow routing table
Load balancers distribute traffic across multiple servers. If one server goes down, traffic is routed to remaining healthy servers. This improves uptime and supports heavy traffic loads.
High jitter on a network is most harmful for
A Offline documents
B Real-time voice
C Local printing
D File renaming
Jitter causes uneven packet arrival times. Voice and video need steady timing, so jitter leads to choppy audio and unstable video. Reducing interference and congestion helps stabilize packet timing.
A cable tester reporting “open” usually indicates
A Wrong DNS
B VLAN mismatch
C Strong Wi-Fi
D Broken wire
“Open” means there is no continuity in one or more conductors. The cable may be cut, poorly crimped, or disconnected. This causes link failures or unstable Ethernet connections.
A “split pair” problem in Ethernet cabling mainly causes
A Strong encryption
B Better latency
C Crosstalk errors
D Higher DHCP
Split pair means wires are on correct pins but not paired correctly. This increases crosstalk and errors, often causing slow speed or unstable links even if the cable appears connected.
If Wi-Fi speed is poor but wired speed is fine, likely cause is
A DNS failure
B Wireless interference
C NAT disabled
D IPv6 missing
Good wired speed proves ISP and router WAN are okay. Poor Wi-Fi points to weak signal, channel congestion, interference, or older Wi-Fi standard. Changing channel/placement often improves results.
A common safe step for router security is to
A Enable open network
B Share WPS PIN
C Disable encryption
D Change admin login
Default router admin credentials are widely known. Changing admin username/password and updating firmware reduces takeover risk. This prevents attackers from changing DNS, opening ports, or disabling security.
A default route on a PC points traffic to the
A DNS server
B Access point
C Default gateway
D Cable tester
The PC sends unknown network traffic to the default gateway. The gateway routes packets to other networks, including the internet. Without a correct default gateway, external access usually fails.
IPv6 is written using
A Hex groups
B Decimal dots
C ASCII art
D Binary only
IPv6 uses hexadecimal groups separated by colons. This represents 128-bit addresses and provides a huge address space, supporting modern network growth better than IPv4.
Subnet masks help decide whether a destination is
A Wired or wireless
B Safe or unsafe
C Local or remote
D Fast or slow
By comparing IP and subnet mask, a device determines if the destination is on the same subnet. If remote, traffic is sent to the default gateway for routing to other networks.
A switch will flood traffic when the destination MAC is
A Known to table
B Same as source
C Always broadcast
D Unknown to table
If the switch doesn’t know which port has the destination MAC, it floods the frame to all ports in that VLAN except the incoming one. It then learns MAC locations from replies.
Excessive broadcast traffic can slow a LAN because it
A Consumes bandwidth
B Encrypts packets
C Shrinks subnets
D Adds IPv6
Broadcasts are delivered to many devices, using bandwidth and CPU processing. Too many broadcasts can create congestion. VLANs and correct network design help reduce unnecessary broadcast traffic.
A broadcast storm often happens due to
A Strong password
B Updated firmware
C Switching loop
D New NIC driver
A loop can cause frames to circulate endlessly and multiply, leading to broadcast storms. Using loop prevention mechanisms and correct cabling prevents storms and network outages.
A WAN link can feel slow even with high bandwidth due to
A Bigger monitors
B More VLANs
C Better DNS
D Packet loss
Packet loss causes retransmissions and delays, reducing effective throughput. Even with high bandwidth, loss can make browsing slow and video calls unstable. Fixing congestion or faulty links improves performance.
The main purpose of a guest network is to
A Share admin access
B Isolate visitors
C Disable firewall
D Lower encryption
Guest networks separate visitor devices from internal devices. Visitors get internet access without reaching shared folders or smart devices. This improves privacy and security, especially in home and office Wi-Fi.
A network documentation diagram should include
A Desktop wallpaper
B Browser bookmarks
C Device connections map
D Screen resolution
Documentation maps devices, links, VLANs, IP ranges, and configurations. This speeds troubleshooting and upgrades by showing how everything is connected and what settings should be used.
A traceroute is especially helpful to find
A Where delay starts
B Wi-Fi password
C MAC address
D VLAN ID
Traceroute lists hops and response times. If delays start after a certain hop, the problem may be beyond that router. This helps narrow down congestion or routing issues along the path.
A ping test primarily checks
A Cable category
B DNS cache size
C SSID length
D Reachability and RTT
Ping sends ICMP echo requests and measures round-trip time. It confirms basic connectivity and highlights high latency or packet loss. It does not prove application services are working.
Wi-Fi channel overlap mainly causes
A Better encryption
B More IP space
C Interference slowdowns
D Faster routing
Overlapping channels cause interference, leading to retransmissions and lower throughput. Choosing a less crowded channel and using 5 GHz (or 6 GHz) reduces overlap and improves Wi-Fi stability.
A modem-router combo device typically provides
A Only MAC learning
B Modem plus routing
C Only hub function
D Only cable testing
Many home devices combine modem and router. They convert ISP line signals and also provide routing, NAT, DHCP, and Wi-Fi access. This simplifies home network setup.
A bridge works mainly at
A Network layer
B Application layer
C Transport layer
D Data link layer
Bridges operate at Layer 2, forwarding frames based on MAC addresses. They connect LAN segments and filter traffic, unlike routers which operate at Layer 3 using IP routing.
A router’s key information source for forwarding is
A MAC table
B DNS cache
C Routing table
D SSID list
Routers consult routing tables to choose the next hop for IP packets. Routing tables contain destination networks and paths, enabling correct packet delivery between different networks.
A switch’s key information source for forwarding is
A MAC address table
B Routing table
C DNS cache
D Subnet mask list
Switches use MAC tables to map addresses to ports. This enables efficient forwarding within a LAN. Unknown MACs lead to flooding until the switch learns the correct port mapping.
A VPN on public Wi-Fi mainly protects against
A Router overheating
B Eavesdropping risk
C VLAN misconfig
D Fiber bending
VPN encrypts traffic, preventing nearby attackers on public Wi-Fi from reading your data easily. It improves privacy for logins and browsing, though safe habits and HTTPS are still important.
If two devices share same IP, the error type is
A DNS conflict
B VLAN conflict
C SSID conflict
D IP conflict
Two devices on the same network using the same IP can cause disconnections and errors. DHCP misconfiguration or overlapping static IP settings commonly cause conflicts. Ensure unique addresses to fix it.
A DHCP reservation uses a device’s
A SSID name
B VLAN ID
C MAC address
D DNS suffix
DHCP reservations map a specific MAC address to a fixed IP. The device still uses DHCP, but always gets the same IP, useful for printers and servers needing consistent addressing.
A safe public Wi-Fi habit is to
A Avoid banking logins
B Disable phone lock
C Share hotspot PIN
D Turn off firewall
Public Wi-Fi can be monitored. Avoid sensitive transactions unless using secure HTTPS and preferably a VPN. Also disable auto-connect and sharing to reduce risk of data theft.
A network speed issue caused by “bottleneck” means
A Fastest link limits
B DNS only limits
C SSID only limits
D Slowest link limits
Overall performance is limited by the slowest segment in the path. Even if most links are fast, a single slow hop or overloaded device can restrict throughput for the entire connection.
When a switch receives a broadcast, it will
A Send to ISP
B Drop always
C Flood within VLAN
D Encrypt it
Broadcast frames are meant for all devices in the broadcast domain. A switch forwards them out all ports in that VLAN. VLAN segmentation limits where broadcasts travel.
A router admin interface should be protected because attackers can change
A Monitor resolution
B DNS and ports
C Keyboard layout
D File names
If attackers access router admin, they can redirect DNS, open ports, disable firewall, or change Wi-Fi security. Strong admin credentials, updates, and disabling remote admin reduce this risk.
The best reason to update router firmware is to
A Increase screen size
B Change cable color
C Reduce RAM usage
D Patch security flaws
Firmware updates fix known vulnerabilities and improve stability. Outdated firmware can be exploited. Keeping firmware updated is a key step along with strong passwords and safe configuration.
A typical sign of bad Ethernet cabling is
A Intermittent link
B Faster ping
C Better upload
D Stronger SSID
Loose or damaged cables can cause link drops, errors, and low speed. Checking connectors, replacing cables, and using a cable tester help confirm physical issues before changing network settings.
Best first troubleshooting action for “no network” is
A Reset DNS first
B Change VLAN now
C Check physical layer
D Disable firewall now
Start with power, cables, link lights, and Wi-Fi connection. Many failures are physical. After confirming the physical layer, then check IP settings, gateway, DNS, and device configuration step-by-step.