100-150 Infrastructure Practice Test 4 — 15 Questions

Question 1

A user reports that they cannot access any network resources, including the internet. A technician checks the user's workstation and finds that it has an IP address of 169.254.10.5 with a subnet mask of 255.255.0.0. The technician verifies that the switch port is active and the cable is connected. What is the most likely cause of the problem?

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

Accepted Answer

The workstation failed to obtain an IP address from a DHCP server.. An IP address in the 169.254.0.0/16 range is an APIPA address, automatically assigned when a DHCP server cannot be reached. This prevents normal network communication. The technician should investigate DHCP server availability, relay agent configuration, or physical connectivity to the DHCP server.

Answer

The workstation has a static IP address that conflicts with another device.

Answer

The default gateway is misconfigured on the workstation.

Answer

The DNS server is unreachable, preventing name resolution.

Question 2

A network administrator is setting up a small office network with a single Cisco router and multiple switches. The administrator wants to ensure that devices on different VLANs can communicate with each other. Which feature should be configured on the router?

Accepted Answer

Router-on-a-stick with subinterfaces. Router-on-a-stick is a technique that uses a single physical router interface with multiple subinterfaces, each configured for a different VLAN. The router then routes traffic between these subinterfaces, enabling inter-VLAN communication. This is an efficient and common solution for small networks where multiple physical router interfaces are not available.

Answer

Spanning Tree Protocol on the router

Answer

Port mirroring on the switch

Answer

Dynamic ARP Inspection on the switch

Question 3

A network engineer is deploying a new Cisco switch and needs to configure it for remote management. The engineer wants to ensure that management traffic is isolated from user data traffic and that only authorized personnel can access the switch. Which two configuration steps should the engineer perform? (Choose two.)

Accepted Answer

Enable SSH and disable Telnet for remote access.. To enable secure remote management, the switch needs an IP address on a management VLAN interface, and remote access should use SSH while Telnet is disabled. These steps provide a reachable management address and ensure that management sessions are encrypted. Other options, like port security or DHCP snooping, address different security concerns and do not fulfill the specific requirements.

Answer

Configure port security on all access ports.

Answer

Configure a default gateway on the switch.

Answer

Enable DHCP snooping on the management VLAN.

Question 4

A network administrator is configuring a Cisco switch and wants to ensure that only the MAC addresses of known devices are allowed to send traffic on a specific access port. The administrator wants to manually specify the allowed MAC addresses and have the port shut down if a violation occurs. Which feature should be configured?

Accepted Answer

Port security with static MAC addresses and violation mode shutdown. Port security is the correct feature to restrict a switch port to specific MAC addresses and take action on violation. Configuring static MAC addresses and setting the violation mode to shutdown ensures that only known devices can communicate, and any violation disables the port. Other features like DAI, 802.1X, and DHCP snooping serve different security purposes.

Answer

802.1X authentication

Answer

DHCP snooping

Answer

Dynamic ARP Inspection (DAI)

Question 5

A network engineer is configuring a Cisco switch and needs to ensure that only the MAC address 00:1A:2B:3C:4D:5E is allowed to communicate through interface GigabitEthernet0/1. The engineer enters the command 'switchport port-security mac-address 00:1A:2B:3C:4D:5E' on the interface. However, the switch rejects the command. What is the most likely cause?

Accepted Answer

Port security has not been enabled on the interface with the 'switchport port-security' command.. Port security must be enabled on an interface before specific secure MAC addresses can be configured. The command 'switchport port-security' activates the feature, allowing subsequent commands like 'switchport port-security mac-address' to be accepted. Without this step, the switch rejects attempts to add secure MAC addresses, as the feature is not active on that port.

Answer

The MAC address format is incorrect; Cisco switches require dot notation.

Answer

The interface is currently in trunk mode, and port security requires access mode.

Answer

Port security must be enabled globally before configuring MAC addresses.

Question 6

A small branch office has a Cisco Layer 2 access switch with three access ports assigned to VLAN 10 for the sales team and two access ports assigned to VLAN 20 for the finance team. The finance team reports that they cannot reach the sales team's shared file server, even though both teams are connected to the same physical switch. No router or Layer 3 switch is deployed at this branch. What is the most likely explanation for the connectivity failure?

Accepted Answer

VLAN 10 and VLAN 20 are separate broadcast domains, and inter-VLAN traffic requires a Layer 3 device that is not present in this topology.. Because VLANs are independent broadcast domains, hosts in VLAN 10 and VLAN 20 cannot exchange traffic at Layer 2 even when they are attached to the same physical switch. Communication between VLANs requires a Layer 3 device to route packets between the subnets. With only a Layer 2 access switch in the branch, no such device exists, so the finance team cannot reach the sales server.

Answer

The switch needs the ip routing global configuration command enabled so that it can forward frames between VLAN 10 and VLAN 20.

Answer

The access ports must be configured as trunk ports so that frames from both VLANs can be carried between them.

Answer

Spanning Tree Protocol has blocked the redundant path between the two VLANs, preventing traffic from flowing between them.

Question 7

A network administrator is troubleshooting a connectivity issue between two hosts on the same VLAN. The administrator uses the 'show mac address-table' command on the switch and notices that the MAC address of one host appears on multiple ports. What is the most likely cause of this behavior?

Accepted Answer

A switching loop exists in the network.. A MAC address appearing on multiple ports is a strong indicator of a switching loop. In a loop, broadcast and unknown unicast frames are flooded endlessly, and the switch learns the source MAC address from different ports as frames traverse the loop in both directions. This causes MAC address flapping, which can destabilize the network.

Answer

Port security is misconfigured and allowing the MAC address on multiple ports.

Answer

The switch's CAM table is corrupted and needs to be cleared.

Answer

The host is connected to multiple switch ports via a dual-homed NIC.

Question 8

A network administrator is troubleshooting a connectivity issue between two switches connected via a trunk link. The administrator notices that the trunk link is up, but VLAN 10 traffic is not passing. The administrator runs the show interfaces trunk command and sees that VLAN 10 is not listed in the 'VLANs allowed and active in management domain' output. What is the most likely cause?

Accepted Answer

VLAN 10 is not allowed on the trunk port.. The show interfaces trunk command displays the VLANs allowed and active on a trunk. If VLAN 10 is missing from that list, it means the trunk configuration is not permitting VLAN 10. The administrator must use the switchport trunk allowed vlan add 10 command to include it. Other issues like missing VLAN creation or native VLAN mismatch would not cause the VLAN to be absent from the allowed list.

Answer

The native VLAN is mismatched on the trunk.

Answer

VLAN 10 is not created on the switches.

Answer

Spanning Tree Protocol is blocking VLAN 10 on the trunk.

Question 9

A technician is deploying a new Cisco switch in a wiring closet and needs to connect it to a distribution switch so that it can carry traffic for VLAN 5, VLAN 15, and VLAN 25 between the two devices. The link must carry frames from all three VLANs simultaneously. Which type of port configuration should be applied to the uplink interface on both switches?

Accepted Answer

A trunk port using 802.1Q encapsulation, which tags frames so multiple VLANs can traverse the single link.. To carry traffic for multiple VLANs across a single physical link between switches, the interface must be configured as a trunk using 802.1Q encapsulation. The trunk tags each frame with its VLAN identifier, keeping VLAN 5, VLAN 15, and VLAN 25 traffic logically separate while sharing the uplink. Access, routed, and SVI configurations each fail to provide this multi-VLAN transport.

Answer

A routed port with an IP address on each VLAN subnet, because routing is required to carry multiple VLANs.

Answer

An access port assigned to VLAN 5, because the native VLAN will automatically carry the other VLANs.

Answer

A switch virtual interface for each VLAN, because SVIs automatically extend VLANs across physical links.

Question 10

A network technician is configuring a new Cisco switch for a small business. The technician needs to ensure that the switch can be managed remotely from a different subnet. Which TWO configurations are required to enable remote management access? (Choose two.)

Accepted Answer

Assign an IP address to a VLAN interface (SVI).. Remote management of a switch from a different subnet requires an IP address assigned to an SVI for network reachability, and a default gateway so the switch can route management traffic off its local subnet. These two configurations provide the necessary Layer 3 connectivity for protocols like SSH or Telnet.

Answer

Enable CDP on all interfaces.

Answer

Set the switch to transparent VTP mode.

Answer

Configure port security on the management interface.

Question 11

A network technician is configuring a Cisco switch for a new VLAN. The technician wants to verify that the VLAN has been created and is active, and also see which ports are assigned to it. Which command should the technician use?

Accepted Answer

show vlan brief. The 'show vlan brief' command provides a concise list of all VLANs, their status, and the ports assigned to each. This directly answers the technician's need to verify VLAN creation and port membership. Other commands like 'show interfaces status' or 'show running-config' provide related but less direct or complete information.

Answer

show mac address-table

Answer

show running-config

Answer

show interfaces status

Question 12

A network engineer is reviewing how a Cisco switch builds and maintains its MAC address table as frames arrive from attached devices. Which TWO statements correctly describe this Layer 2 forwarding behavior? (Choose two.)

Accepted Answer

If the destination MAC address is not in the table, the switch floods the frame out all ports except the one it arrived on.. A Layer 2 switch learns by examining the source MAC address of each incoming frame and mapping it to the ingress port. When the destination MAC is absent from the table, the switch floods the frame out all other ports in the VLAN so delivery can still occur. These two behaviors together allow the table to populate dynamically and traffic to be forwarded efficiently once paths are known.

Answer

The switch forwards a frame only after the entire frame has been received and the CRC verified, regardless of configuration.

Answer

The switch assigns an IP address to each connected device and stores it in the MAC address table.

Answer

MAC address table entries are permanent and are never removed unless the administrator manually clears them.

Question 13

A network administrator is reviewing the MAC address table on a Cisco access switch and notices that the same MAC address appears on two different access ports in the same VLAN. The administrator confirms that the device with that MAC address is connected to only one port. What is the most likely cause of this duplicate entry?

Accepted Answer

A switching loop exists in the VLAN, causing frames to be learned on multiple ports as they circulate.. A duplicate MAC address entry on two ports in the same VLAN is a classic symptom of a Layer 2 switching loop. Frames circulate through the redundant path, and the switch learns the device's MAC address from frames arriving on different ports. Spanning Tree Protocol normally prevents this by blocking redundant links, so the administrator should verify STP operation and check for unauthorized devices creating loops.

Answer

The device is using a virtual MAC address for redundancy, so the switch learns it on every port in the VLAN.

Answer

The MAC address table has reached its aging time and is flushing entries faster than they can be relearned.

Answer

Port security has been configured with a sticky MAC address, which copies the address to all ports in the VLAN.

Question 14

A network engineer is configuring a Cisco router interface that connects to an ISP. The ISP has assigned the engineer a single public IP address of 203.0.113.10 with a subnet mask of 255.255.255.252 and a default gateway of 203.0.113.9. The engineer needs to configure the router interface with the correct IP address and mask. Which configuration should be applied?

Accepted Answer

ip address 203.0.113.10 255.255.255.252. The ISP assigned a /30 subnet, so the correct mask is 255.255.255.252. Within 203.0.113.8/30, the usable host addresses are 203.0.113.9 and 203.0.113.10, and the gateway uses 203.0.113.9. The router interface must therefore be configured with 203.0.113.10 and the /30 mask to be in the same subnet as the ISP gateway and establish connectivity.

Answer

ip address 203.0.113.9 255.255.255.252

Answer

ip address 203.0.113.10 255.255.255.0

Answer

ip address 203.0.113.10 255.255.255.248

Question 15

A network administrator is deploying a new Cisco switch in a small office and wants to apply basic security hardening to protect the management plane. The administrator plans to restrict remote access and prevent unauthorized configuration changes. Which two actions should the administrator take to secure management access to the switch? (Choose two.)

Accepted Answer

Configure a strong enable secret and use local usernames with privilege levels for authentication.. Securing the management plane requires strong authentication and restricted access. Configuring an enable secret with local usernames and privilege levels ensures only authenticated administrators can reach privileged EXEC mode. Applying an access list to the VTY lines limits remote management sessions to trusted source subnets. Together these controls protect the switch from unauthorized configuration changes and remote access attempts.

Answer

Assign the management VLAN to an unused access port and leave it in the default VLAN 1.

Answer

Enable Telnet on all VTY lines so that administrators can manage the switch from any network segment.

Answer

Configure the switch to use the default enable password with no secret so that recovery is easier.