220-1101 Networking Practice Test 3 — 15 Questions

Question 1

A small office has 12 computers connected to a single unmanaged switch, which is connected to a router providing internet access. Users report that at random times, all computers lose internet connectivity for a few seconds, then it returns. The technician observes that when the problem occurs, the lights on the switch do not change, but a Ping to the router fails. The technician has replaced the router and the switch, but the issue persists. Which of the following is the MOST likely cause?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

A: A bad Ethernet cable between the switch and router. A faulty cable between the switch and router is the most likely cause. All computers lose internet simultaneously because the uplink to the router is the shared path. The switch lights remaining unchanged suggests the link is still up, but a marginal cable can cause intermittent packet loss or corruption. Since the router and switch were replaced but the cable was not, the issue persists. A rogue DHCP server would affect clients individually during lease renewals, wouldn't cause synchronized outages across all computers, and the effect would usually last longer than a few seconds.

Answer

B: A user's device acting as a rogue DHCP server

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C: A failing network card in one of the computers

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D: A misconfigured firewall rule on the router

Question 2

A technician is troubleshooting a user's workstation that can ping other computers on the local network but cannot access any websites. The user's router is configured with DHCP and DNS is set to automatic. The technician runs ipconfig /all and sees the workstation has an IP address of 192.168.1.45 with a subnet mask of 255.255.255.0 and a default gateway of 192.168.1.1. The technician successfully pings 8.8.8.8 from the workstation. Which of the following is the MOST likely cause of the issue?

Accepted Answer

The workstation has a manually configured DNS server that is unreachable. The workstation can ping 8.8.8.8 (a public IP address) successfully, which confirms that IP routing, the default gateway, and the physical network layer are all working correctly. However, it cannot access websites by name, which points to a DNS resolution failure. Since the router is set to automatic DNS but the workstation has a manually configured DNS server that is unreachable, the workstation will fail to resolve domain names into IP addresses, even though it can reach external IPs directly.

Answer

The subnet mask is incorrect

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The network cable is faulty

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The router's DHCP server has exhausted its IP address pool

Question 3

A technician is troubleshooting an issue where users in one department cannot access the internet, but they can access shared files on the local network. The router's status lights indicate WAN connectivity is active. Which of the following should the technician check FIRST?

Accepted Answer

Faulty network cable from the department switch to the router. The symptom of a whole department losing internet while retaining local access points to an issue between the department switch and the router. The router's WAN light being active only indicates connectivity to the ISP, not to the internal network. A faulty LAN cable (D) would prevent users from reaching the default gateway, causing exactly these symptoms. DNS misconfiguration (A) is possible but typically affects name resolution only, and would not be the first check when physical connectivity is in question. Troubleshooting methodology dictates checking physical layer issues before higher-layer causes.

Answer

DNS server settings on the affected computers

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DHCP scope exhaustion

Answer

Firewall settings on the router

Question 4

A technician is troubleshooting a user's laptop that connects to the corporate Wi-Fi network successfully and obtains a valid IP address in the 192.168.x.x range. However, the user cannot access the internet or any internal servers. Other devices on the same Wi-Fi network are working fine. Which of the following should the technician check FIRST?

Accepted Answer

The DNS server settings. The laptop has a valid IP address and connects to Wi-Fi, while other devices work, isolating the problem to the laptop's configuration. Since the issue affects both internet and internal servers, a likely cause is incorrect DNS settings, which can prevent name resolution. Checking DNS settings first is a standard troubleshooting step because it quickly tests a common cause of total access failure. The network profile type would not block all outbound traffic, so it is not the best first check.

Answer

The laptop's network profile type

Answer

The DHCP server's IP address pool

Answer

The default gateway's MAC address

Question 5

A technician is troubleshooting a user's workstation that intermittently loses network connectivity. The user says the connection drops for a few seconds and then reconnects. The technician checks the switch port and sees a high number of runt frames. The Ethernet cable is properly connected and passes a cable tester. Which of the following is the MOST likely cause?

Accepted Answer

Duplex mismatch between the workstation and the switch. A duplex mismatch occurs when one device (e.g., the workstation) is set to auto-negotiate while the other (the switch port) is manually set to full-duplex, or vice versa. This causes the switch to detect runt frames (frames smaller than 64 bytes) due to collisions on a half-duplex link, leading to intermittent connectivity drops. The cable passing the tester and the high runt count point directly to a Layer 1/2 negotiation issue, not a physical cable fault.

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Faulty network interface card (NIC)

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Electromagnetic interference (EMI) near the cable

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Incorrect VLAN assignment on the switch port

Question 6

A technician is troubleshooting a small office network. Users on one side of the office report very slow network speeds and occasional disconnections. The technician checks the unmanaged switch and notices that the link LED for the port connected to a particular workstation is rapidly alternating between green and amber. The workstation is able to obtain an IP address. Which of the following is the MOST likely cause of this issue?

Accepted Answer

Faulty patch cable connecting the workstation to the wall jack. The rapidly alternating green and amber link LED on an unmanaged switch indicates that the link is constantly renegotiating speed/duplex. This is a classic symptom of a faulty or marginal cable, causing intermittent connectivity and errors, which would lead to slow speeds and disconnections. The workstation can still obtain an IP address because the link is sometimes up enough for DHCP. A duplex mismatch typically produces a stable link (solid LED) with high error rates, not rapid color alternation. An IP conflict would not affect the physical-layer LED, and overheating would affect the entire switch, not just one port.

Answer

Duplex mismatch between the switch and the workstation

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IP address conflict with another device on the network

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The switch is overheating due to poor ventilation

Question 7

A network technician is troubleshooting a new fiber optic link between two buildings. The link is down. The technician uses a visual fault locator (VFL) at the transmitting end and observes a faint red glow at the patch panel in the receiving building. What does this indicate?

Accepted Answer

The fiber has a break or severe bend. A faint red glow from a visual fault locator (VFL) at the far-end patch panel indicates that visible laser light is leaking from the fiber due to a break or severe bend. VFLs inject a high-power visible red laser (typically 650 nm) into the core. If the fiber is intact, the light travels to the far end and emerges brightly from the connector. A faint glow at the far end means much of the light has escaped before reaching the end, due to a physical defect such as a break or severe bend, confirming a fault that prevents proper data transmission.

Answer

The fiber connectors are dirty

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The transmitter power is too low

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The connectors are mismatched (e.g., SC vs. LC)

Question 8

A small office network uses a single router connected to a managed switch. The technician has configured two VLANs on the switch: VLAN 10 for Sales and VLAN 20 for Engineering. Both VLANs can access the internet, but devices in Sales cannot reach devices in Engineering. The router has one physical interface connected to the switch. The technician configured a subinterface on the router for each VLAN with appropriate IP addresses. However, devices on VLAN 20 cannot access the internet, while VLAN 10 works fine. Which of the following is the MOST likely missing configuration?

Accepted Answer

The switch port connecting to the router is not configured as a trunk port. The router uses subinterfaces for VLAN routing, which requires the switch port connecting to the router to be configured as a trunk port (802.1Q trunking). Without trunking, the switch port will only carry traffic from a single VLAN (likely VLAN 1 or the native VLAN), so VLAN 20 frames are dropped at the switch-to-router link. This explains why VLAN 10 works (if it matches the access VLAN on that port) and VLAN 20 fails to reach the internet.

Answer

The router's DHCP server is not configured for VLAN 20

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The firewall on the router is blocking all traffic from VLAN 20

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The VLAN 20 subinterface is not assigned a gateway IP address

Question 9

A network technician is configuring a small office network with one router and one managed switch. The network has two VLANs: VLAN 10 (Sales) and VLAN 20 (Engineering). Both VLANs need internet access, and inter-VLAN routing is not required. The technician configures the router's single physical interface with IP 192.168.1.1/24 and creates subinterfaces for VLAN 10 (192.168.10.1/24) and VLAN 20 (192.168.20.1/24). The switch port connecting to the router is configured as an access port in VLAN 10. Which of the following is the MOST likely result?

Accepted Answer

Neither VLAN can access the internet.. The router's subinterfaces are configured for VLAN 10 and VLAN 20, but the switch port connecting to the router is an access port in VLAN 10. Access ports carry only untagged traffic and drop tagged frames. Therefore, frames sent by the router's subinterfaces (which are tagged with VLAN 10 or 20) will be dropped by the switch. Conversely, frames sent by hosts in either VLAN arrive at the router untagged, so they are associated with the physical interface (192.168.1.1/24), not the subinterfaces (192.168.10.1 or 192.168.20.1). Consequently, neither VLAN can communicate with the router's subinterface IPs, and neither VLAN can access the internet.

Answer

Only VLAN 10 can access the internet; VLAN 20 cannot.

Answer

Both VLANs can access the internet.

Answer

Only VLAN 20 can access the internet; VLAN 10 cannot.

Question 10

A small office recently installed 12 new VoIP phones. Each phone is connected via an Ethernet cable to a 24-port managed PoE+ switch. The switch is powered on, and the network cables are properly terminated. However, none of the VoIP phones power on. The switch's power LED is solid, but the port LEDs remain off. Which of the following is the MOST likely cause?

Accepted Answer

The switch's PoE power budget has been exceeded. The switch's power LED is solid, indicating it has power, but the port LEDs are off, meaning no devices are being powered. Since all 12 VoIP phones are connected to a 24-port PoE+ switch, the most likely cause is that the total power draw of 12 phones exceeds the switch's PoE power budget. PoE+ (802.3at) provides up to 30W per port, but the switch has a limited total power supply (e.g., 250W), and 12 phones at 15-30W each could easily exceed that budget, causing the switch to deny power to all ports.

Answer

The switch ports are configured as access ports for a specific VLAN

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The Ethernet cables are only Category 5 (Cat5)

Answer

The phones require a higher voltage than PoE+ provides

Question 11

A network technician configures a managed switch with two VLANs: VLAN 10 (Marketing: 192.168.10.0/24) and VLAN 20 (Engineering: 192.168.20.0/24). The switch is connected to a router via a single trunk port. The router has subinterfaces configured: G0/0.10 with IP 192.168.10.1/24 and G0/0.20 with IP 192.168.20.1/24. A workstation in Marketing can ping its own default gateway (192.168.10.1) but cannot ping the Engineering gateway (192.168.20.1). Which of the following is the MOST likely cause?

Accepted Answer

The switch port connecting to the router is configured as an access port in VLAN 10. The workstation in Marketing can ping its own gateway (192.168.10.1) because that subnet is directly reachable via the switch. However, it cannot ping the Engineering gateway (192.168.20.1) because the switch port connecting to the router is configured as an access port in VLAN 10. This forces all traffic from the router to the switch to be untagged and only in VLAN 10, so frames destined for VLAN 20 are dropped or misdelivered. A trunk port with 802.1Q encapsulation is required to carry both VLANs over the single link.

Answer

The router's subinterface G0/0.20 is not configured with the correct encapsulation

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The workstation in Marketing has an incorrect subnet mask

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The routing table on the router does not have routes for the Engineering subnet

Question 12

A small office recently installed eight new VoIP phones. Each phone is connected via an Ethernet cable to a 24-port managed PoE+ switch. The switch is powered on, and the network cables are properly terminated. However, none of the VoIP phones power on. The switch's power LED is solid, but the port LEDs for the connected phones remain off. The technician verifies that the PoE budget of the switch (240W) is sufficient for all eight phones (each requiring 6.5W). Which of the following is the MOST likely cause?

Accepted Answer

PoE is disabled on the switch ports or globally.. The most likely cause is that PoE is disabled on the switch ports or globally. Even though the switch supports PoE+ and has sufficient power budget, PoE may be administratively disabled per port or globally (e.g., via the 'power inline never' command on Cisco switches). The solid power LED indicates the switch is powered, but the off port LEDs show no power is being delivered to the phones, which is consistent with PoE being administratively disabled.

Answer

The Ethernet cables are not PoE-compatible.

Answer

The VLAN configuration on the switch is preventing the phones from receiving power.

Answer

The switch's power supply cannot supply enough total wattage.

Question 13

A user reports that they cannot access any websites through their web browser, but they can access shared files on the local network and can successfully ping 8.8.8.8 from the command prompt. The technician checks the IP configuration and finds the workstation has a valid IP address, subnet mask, and default gateway. The DNS server is set to 8.8.8.8. Which of the following is the MOST likely cause of the issue?

Accepted Answer

The web browser proxy settings are configured incorrectly, preventing internet access. The user can ping 8.8.8.8, confirming IP connectivity to a public address, and can access local shares, confirming LAN connectivity. However, a ping to an IP does not test DNS resolution, as no hostname is resolved. The DNS server is set to 8.8.8.8, but being able to ping it does not guarantee that DNS queries succeed. The most likely cause of the browser being unable to load websites while other network functions work is incorrect proxy settings in the web browser. If the browser is configured to use a proxy server that is unreachable or misconfigured, all web requests fail, while applications that do not use the browser's proxy (e.g., ping, file sharing) continue to operate normally. A firewall rule blocking ports 80 and 443 could also cause this, but it is less likely when only one workstation is affected and would not explain why the browser specifically fails while other network utilities work. Therefore, B is the most likely answer.

Answer

A firewall rule is blocking all outbound traffic on ports 80 and 443

Answer

The DNS suffix search order is misconfigured

Answer

The ARP cache is corrupted, preventing the workstation from communicating with the default gateway

Question 14

A small office uses a single router with DHCP enabled for 50 devices. Recently, some devices cannot obtain an IP address, while others work fine. The technician checks the DHCP lease table and sees that it is nearly full with 49 active leases. The network uses a default Class C subnet (255.255.255.0). Which of the following is the MOST appropriate solution to ensure all devices can obtain an IP address in the future?

Accepted Answer

Increase the DHCP scope size by changing the subnet mask to /23 (255.255.254.0).. The default Class C subnet mask /24 (255.255.255.0) provides 254 usable IP addresses, but the DHCP pool is often configured as a smaller range (e.g., 192.168.1.100–192.168.1.199). With 49 active leases out of a typical default pool of 50–100 addresses, the pool is nearly exhausted. Changing the subnet mask to /23 (255.255.254.0) expands the network to 510 usable addresses, allowing the DHCP pool to be enlarged and ensuring all 50 devices can obtain IP addresses without exhausting the pool.

Answer

Change the router's LAN IP address to a different private subnet, such as 10.0.0.1/8.

Answer

Reduce the DHCP lease time so that addresses are recycled more frequently.

Answer

Disable DHCP on the router and assign static IP addresses to all devices.

Question 15

A user reports that their workstation cannot access the internet or any network resources. The technician runs ipconfig and sees the IP address 169.254.10.55 with subnet mask 255.255.0.0. The Ethernet link lights are solid on both the NIC and the switch port. Which of the following is the MOST likely cause?

Accepted Answer

DHCP server is unavailable. The IP address 169.254.10.55 with subnet mask 255.255.0.0 is an Automatic Private IP Addressing (APIPA) address, assigned by Windows when a DHCP server is unavailable. Since the link lights are solid, the physical layer is functional, but the workstation cannot obtain a valid IP address, indicating the most likely cause is a DHCP server failure or misconfiguration.

Answer

The DNS server is unreachable

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The default gateway is misconfigured

Answer

The network cable is faulty