220-1101 Networking — 15 Questions

Question 1

A technician is adding a wireless access point (AP) in an outbuilding connected via Ethernet to the main office network (192.168.1.0/24). After configuring the AP with a static IP of 192.168.1.250, clients can connect to Wi-Fi but cannot access the internet. The main office devices have no issues. What is the most likely cause?

Accepted Answer

The new AP has its DHCP server enabled. The most likely cause is that the new AP has its DHCP server enabled. When the AP assigns IP addresses to clients via its own DHCP, those clients receive an IP address from a different subnet or scope than the main office network (192.168.1.0/24). This prevents them from reaching the default gateway (e.g., 192.168.1.1) and thus the internet, while the AP itself remains reachable on its static IP. Disabling the AP's DHCP server and allowing clients to obtain addresses from the main network's DHCP server resolves the issue.

Answer

The SSID on the new AP differs from the main network's SSID

Answer

The Ethernet cable connecting the AP is a crossover cable

Answer

The switch feeding the AP is not configured for VLAN 1

Question 2

A small office has a DHCP server that assigns IP addresses in the range 192.168.1.100 to 192.168.1.200. A file server needs a static IP address of 192.168.1.10. Which method should the technician use to ensure the server always receives that IP address without manually configuring the network adapter on the server?

Accepted Answer

Create a DHCP reservation on the router for the server's MAC address. A DHCP reservation binds a specific IP address to a client's MAC address on the DHCP server (often integrated into the router). This ensures the file server always receives 192.168.1.10 from the DHCP server without requiring manual configuration on the server itself, which is the requirement in the question. The reservation works because the DHCP server checks the MAC address in the DHCP request and always offers the reserved IP.

Answer

Configure the server with a static IP address of 192.168.1.10 in the operating system settings

Answer

Change the DHCP range to 192.168.1.11-200 so that .10 is excluded

Answer

Set up a port forwarding rule for the server

Question 3

A company has a router with four Ethernet ports. They need to connect 12 wired devices in the same LAN segment. All devices must receive IP addresses from the same DHCP server running on the router. Which device should the technician add?

Accepted Answer

Switch. A switch is the correct device because it operates at Layer 2 of the OSI model, forwarding Ethernet frames based on MAC addresses, and can connect multiple devices while keeping them in the same broadcast domain. With four router ports already in use, adding a switch allows the 12 wired devices to share a single LAN segment and receive IP addresses from the router's DHCP server, as the switch transparently forwards DHCP broadcast traffic.

Answer

Hub

Answer

Access point

Answer

Modem

Question 4

A technician installs a new VoIP phone that receives power via PoE from a managed switch. The phone powers on but cannot register with the call server. A PC connected to the phone's passthrough port obtains an IP address and accesses the internet normally. Which of the following is the most likely cause of the phone's failure?

Accepted Answer

The switch port has a VLAN mismatch for the voice VLAN. The phone powers on via PoE and the PC behind it works, proving Layer 1 and basic Layer 2 connectivity are fine. The phone cannot register with the call server, which typically requires it to be on the correct voice VLAN. A VLAN mismatch for the voice VLAN means the switch port is configured to tag voice traffic with a different VLAN ID than the phone expects, preventing the phone from communicating with the call server.

Answer

The switch port is configured with a voice VLAN that the phone is not using

Answer

The Ethernet cable between the switch and the phone is faulty

Answer

The phone's MAC address is filtered on the network

Question 5

A network technician is troubleshooting a connectivity issue in a small office. A user's computer obtains an IP address starting with 169.254.x.x. The network uses DHCP from a router with IP 192.168.1.1. The technician checks the cable and sees the link light is on. The computer was working yesterday. Which of the following is the most likely cause?

Accepted Answer

The DHCP server has exhausted its IP pool. The 169.254.x.x address is an Automatic Private IP Addressing (APIPA) address, assigned by Windows when DHCP fails. Since the computer worked yesterday and the link light is on, the most likely cause is that the DHCP server's IP pool is exhausted, preventing new leases. This is a common scenario in small offices with limited IP ranges.

Answer

The DHCP server's IP address changed

Answer

The network cable is a crossover cable

Answer

The computer's network adapter is faulty

Question 6

A technician is replacing a 10/100 Mbps network switch with a new Gigabit switch. After connecting all devices, the technician notices that the link LEDs on several ports are showing amber instead of green. The switch documentation states that green indicates a 1000 Mbps link, and amber indicates a 10/100 Mbps link. All connected devices support Gigabit Ethernet. Which of the following is the MOST likely cause of this issue?

Accepted Answer

The Ethernet cables between the switch and devices are faulty or of poor quality.. The amber link LED indicates that the switch is operating at 10/100 Mbps rather than the expected 1000 Mbps. Since all connected devices support Gigabit Ethernet, the most likely cause is that the Ethernet cables are faulty or of poor quality, as Gigabit Ethernet requires all four twisted pairs (8 wires) to be fully functional, whereas 10/100 Mbps only uses two pairs. A marginal or damaged cable can cause auto-negotiation to fall back to a lower speed.

Answer

The devices are configured for half-duplex, causing auto-negotiation to fail.

Answer

The power supply of the switch is insufficient for all ports.

Answer

The switch is not properly configured for Gigabit mode.

Question 7

A user reports that their laptop can see the company's Wi-Fi SSID but cannot connect to the network. Other users in the same area can connect without issues. The technician verifies that the laptop's wireless adapter is enabled and that the wireless security key is correct. Which of the following should the technician check NEXT?

Accepted Answer

MAC filtering settings on the wireless router. Since other users can connect to the same SSID, the DHCP server and wireless channel are not the issue. The laptop can see the SSID and the security key is correct, so authentication is passing, but association is failing. MAC filtering blocks the laptop's MAC address at Layer 2, preventing it from obtaining an IP address even with correct credentials.

Answer

The DHCP server to ensure IP addresses are available

Answer

The DNS server configuration on the laptop

Answer

Wireless channel interference from other devices

Question 8

A technician is setting up a small network with a router, a 24-port unmanaged switch, and 15 computers. The router's DHCP server assigns IP addresses in the 192.168.1.0/24 range. All computers get valid IP addresses and can access the internet, but they cannot see each other in the network discovery list. Which of the following is the MOST likely cause?

Accepted Answer

Network discovery and file sharing are disabled on the computers. The computers can access the internet and receive valid IP addresses from the router's DHCP server, indicating that Layer 3 connectivity is working. However, they cannot see each other in the network discovery list, which is a Layer 2/application-layer feature. Network discovery relies on the Function Discovery Resource Publication (FDResPub) and SSDP protocols, and file sharing relies on the SMB protocol; both are typically disabled by default on Windows machines for security reasons. Enabling network discovery and file sharing in the Network and Sharing Center resolves the visibility issue.

Answer

The switch is not configured with VLANs

Answer

The subnet mask is set to 255.255.0.0

Answer

The router's firewall is blocking LAN traffic

Question 9

An ISP provides a cable modem with a single Ethernet port. A technician needs to set up a small office network with 25 workstations that require internet access and must be on the same subnet. The technician has a 24-port unmanaged switch and a 48-port unmanaged switch. Which of the following is the MOST appropriate method to connect the devices?

Accepted Answer

Connect both switches to a router, and connect the modem to the router.. Option B is correct because a router is required to perform Network Address Translation (NAT) and routing between the ISP's public IP and the private subnet. The cable modem provides only a single Ethernet port and does not route traffic between multiple devices; connecting both switches to a router allows all 25 workstations to share the internet connection while remaining on the same subnet. The router acts as the default gateway and DHCP server, enabling proper IP address assignment and traffic forwarding.

Answer

Connect the modem directly to the 48-port switch and then daisy-chain the 24-port switch from the 48-port switch.

Answer

Connect the modem to the 24-port switch, then connect the 48-port switch to the 24-port switch.

Answer

Connect the modem directly to the 48-port switch and connect the 24-port switch to the 48-port switch.

Question 10

A small office has a router that provides DHCP services. Several users report that they cannot access the internet, but they can still access shared folders on the local network. The technician checks one user's computer and sees an IP address of 169.254.10.25. Which of the following is the MOST likely cause of the issue?

Accepted Answer

The DHCP server is not responding. The IP address 169.254.10.25 falls within the Automatic Private IP Addressing (APIPA) range (169.254.0.0/16), which Windows assigns when a DHCP discovery broadcast fails to receive a response. Since users can still access local shared folders, local link-layer connectivity is intact, but the lack of a valid DHCP lease means they have no default gateway or DNS server configuration, preventing internet access. The most likely cause is that the DHCP server (the router) is not responding to DHCP requests.

Answer

The DNS server is not resolving domain names

Answer

The default gateway is misconfigured

Answer

A duplicate IP address exists on the network

Question 11

A network technician is installing a new IP security camera that requires Power over Ethernet (PoE) IEEE 802.3af. The technician runs a new Cat6 Ethernet cable between a PoE switch port and the camera. The switch is PoE-enabled and configured to supply power. When the camera is connected, it does not power on. The technician tests the cable with a continuity tester, and all eight wires pass. Which of the following is the most likely cause of the issue?

Accepted Answer

The switch port is administratively disabled in the switch configuration.. The most likely cause is that the switch port is administratively disabled. Even though the switch is PoE-enabled and the cable passes continuity, if the port is in a shutdown state (e.g., via the 'shutdown' command in Cisco IOS), it will not provide power or data to the camera. The technician should verify the port status with 'show interfaces' or 'show running-config' and enable it with 'no shutdown'.

Answer

The cable run exceeds the maximum length for PoE (100 meters).

Answer

The camera requires PoE+ (802.3at) and will not work with standard PoE.

Answer

The cable is terminated with T568A on one end and T568B on the other.

Question 12

A network administrator configures a new managed switch with 24 ports. All ports are in the same VLAN (VLAN 1) by default. The administrator then changes ports 1-12 to VLAN 10 and ports 13-24 to VLAN 20. Computers connected to ports in different VLANs are assigned IP addresses from the same DHCP server. Which of the following is a direct consequence of this configuration?

Accepted Answer

Computers in different VLANs cannot communicate unless a router is configured. VLANs segment a network at Layer 2, isolating broadcast domains. Without a router or Layer 3 switch configured for inter-VLAN routing, devices in different VLANs cannot communicate because they are on separate subnets and the switch will not forward frames between VLANs. The DHCP server can still assign IP addresses if it is connected to a port that is a member of both VLANs (e.g., a trunk port) or if a DHCP relay (ip helper-address) is configured on the router, but direct Layer 2 communication between VLANs is impossible without a routing device.

Answer

Computers in different VLANs can communicate directly at Layer 2

Answer

The switch will forward traffic between VLANs using internal routing

Answer

DHCP requests from VLAN 20 will be dropped by the switch

Question 13

A technician is setting up a small office network with a router that has integrated DHCP and a 24-port unmanaged switch. All computers are connected to the switch. Users report that they can access the internet but cannot see each other in Network Neighborhood. The technician checks and finds that all computers have IP addresses in the 192.168.1.0/24 range but with different subnet masks: some have 255.255.255.0, others have 255.255.0.0. Which of the following is the most likely cause?

Accepted Answer

The DHCP server is not assigning the correct subnet mask.. The DHCP server is configured to hand out IP addresses in the 192.168.1.0/24 range, but it is assigning inconsistent subnet masks (some /24, some /16). This causes computers with different subnet masks to calculate different network portions of their IP addresses, preventing them from seeing each other in Network Neighborhood even though they can reach the internet through the router's default gateway.

Answer

The switch is not forwarding broadcasts.

Answer

The router's firewall is blocking local traffic.

Answer

The computers are using different default gateways.

Question 14

A technician is setting up a small office network with a wireless router serving as the DHCP server and an unmanaged 24-port switch. All desktop computers are connected to the switch via Ethernet cables. The computers can access the internet without any issues, but they cannot see each other in the network discovery list or ping each other by IP address. The technician checks the IP configuration on one computer and finds it has an IP address of 192.168.1.10 with a subnet mask of 255.255.255.0. The technician can ping the router (192.168.1.1). Which of the following is the MOST likely cause of this issue?

Accepted Answer

The Windows firewall on each computer is blocking inbound connections.. The computers can access the internet and ping the router, confirming that the DHCP server is correctly assigning IP addresses, subnet masks, and default gateways, and that the switch is forwarding traffic properly. The inability to ping each other by IP address or see each other in network discovery strongly indicates that the Windows firewall on each computer is blocking inbound ICMP and NetBIOS/LLMNR traffic, which are required for ping responses and network discovery. This is a common default behavior of Windows Firewall in certain network profiles (e.g., Public), which blocks inbound connections unless explicitly allowed.

Answer

The DHCP server is not assigning the correct default gateway.

Answer

The switch is not properly forwarding broadcast traffic between ports.

Answer

The computers are receiving IP addresses from different VLANs.

Question 15

A user reports that their desktop computer can access shared files on the local network but cannot reach the internet. The technician checks the IP configuration and sees the address 169.254.25.100 with a subnet mask of 255.255.0.0. Other computers on the same subnet can access the internet normally. Which of the following is the MOST likely cause?

Accepted Answer

A. The IP address 169.254.25.100 with a subnet mask of 255.255.0.0 is an Automatic Private IP Addressing (APIPA) address, assigned by Windows when a DHCP server cannot be reached. Since other computers on the same subnet can access the internet normally, the DHCP server is functional, so the issue is specific to this computer's inability to obtain a valid DHCP lease. The most likely cause is a faulty or disconnected Ethernet cable, which prevents the computer from communicating with the DHCP server, causing it to fall back to APIPA.

Answer

B

Answer

C

Answer

D