100-150 Infrastructure — 15 Questions

Question 1

Which component of the Cisco network architecture is responsible for providing high-speed switching and fast transport between different areas of the network?

Accepted Answer

Core Layer. The Cisco three-layer hierarchical model includes the Core, Distribution, and Access layers. The Core layer is specifically designed for high-speed switching and transport. It provides a reliable, high-bandwidth backbone that connects different parts of the enterprise, ensuring that traffic is moved across the network with minimal latency and high availability.

Answer

Access Layer

Answer

Distribution Layer

Answer

Edge Layer

Question 2

A technician is connecting a new Cisco Catalyst access switch to an existing IDF patch panel. The run to the distribution switch is approximately 60 meters through a cable tray that also carries fluorescent lighting ballasts. The technician needs a cable that supports 1 Gbps and is immune to the electromagnetic interference generated in the tray. Which cable type should be used?

Accepted Answer

Multimode fiber with LC connectors. Fiber optic cabling transmits light instead of electrical signals, which means it cannot be affected by the electromagnetic interference radiated by fluorescent ballasts sharing the same tray. Multimode fiber also comfortably exceeds the 60-meter distance while delivering 1 Gbps. Copper options, whether shielded or not, remain vulnerable to conducted noise in that environment.

Answer

Cat 3 UTP

Answer

Cat 5e UTP

Answer

Cat 6a UTP

Question 3

A network engineer is designing a small office network that requires high-speed connections between switches and to a server. The engineer wants to use Ethernet technology that supports full-duplex communication and can operate over twisted-pair copper cabling. Which two Ethernet standards meet these requirements? (Choose two.)

Accepted Answer

10GBASE-T. 1000BASE-T and 10GBASE-T are Ethernet standards that operate over twisted-pair copper cabling and support full-duplex communication. 1000BASE-T provides 1 Gbps, while 10GBASE-T provides 10 Gbps, both suitable for high-speed connections. The other options either use fiber optic cabling or do not provide sufficient speed for the described requirements.

Answer

1000BASE-SX

Answer

100BASE-TX

Answer

100BASE-FX

Question 4

A network administrator is troubleshooting connectivity issues on a Cisco switch. A workstation connected to port FastEthernet 0/5 cannot reach the file server on the same VLAN. The administrator runs the 'show interface FastEthernet 0/5' command and sees the following output: 'FastEthernet0/5 is up, line protocol is down'. What is the most likely cause of the problem?

Accepted Answer

The VLAN assigned to the port is not active or does not exist.. The output 'up, line protocol is down' indicates that the physical layer is operational but the data link layer is not. On a Cisco switch, this often occurs when the VLAN assigned to the port is not active or does not exist. The switch cannot forward frames without a valid VLAN, so the line protocol goes down.

Answer

The workstation's network interface card is disabled.

Answer

There is a speed or duplex mismatch between the switch port and the workstation.

Answer

The cable is faulty or not connected properly.

Question 5

A network administrator is planning the IPv4 addressing for a small branch office that will contain 45 hosts on a single subnet. The administrator wants to conserve addresses and use the smallest subnet mask that still accommodates all hosts. Which subnet mask should be configured?

Accepted Answer

255.255.255.224. Supporting 45 hosts requires at least 6 host bits, because 2^6 minus 2 equals 62 usable addresses, while 5 host bits give only 30. Six host bits correspond to a /26 mask, written as 255.255.255.192. This is the smallest subnet that accommodates the branch while minimizing wasted addresses.

Answer

255.255.255.192

Answer

255.255.255.0

Answer

255.255.255.128

Question 6

A network administrator is configuring a Cisco router interface that connects to an ISP. The link must obtain its IPv4 address automatically from the provider rather than using a static configuration. Which command should be applied to the interface to accomplish this?

Accepted Answer

ip address dhcp. To make a router interface request its addressing dynamically from a service provider, the interface must run as a DHCP client using the ip address dhcp command. This obtains the address, subnet mask, and often a default gateway and DNS servers. It is the appropriate choice for an Ethernet WAN handoff where the ISP assigns addressing automatically.

Answer

ip address negotiated

Answer

ip dhcp pool

Answer

ip helper-address

Question 7

A network technician is connecting a new Cisco Catalyst switch to an existing switch using a copper cable. The link fails to come up, and the interface status shows 'notconnect'. The technician verifies the cable is a straight-through Ethernet cable and that both switches use auto-MDIX. Which action should the technician take to resolve the problem?

Accepted Answer

Check the cable for damage and reseat the connectors on both ends.. The interface status 'notconnect' indicates a physical layer problem, meaning the switch port is not receiving a link signal. Auto-MDIX eliminates the need for a crossover cable, so the cable type is not the cause. The most likely culprits are a damaged cable or poor physical connection. Verifying and reseating the cable is the appropriate troubleshooting step before investigating more complex issues like speed/duplex or administrative state.

Answer

Verify that the interface is not administratively shut down.

Answer

Configure the interface speed and duplex settings to match on both switches.

Answer

Replace the straight-through cable with a crossover cable.

Question 8

A network administrator is configuring a Cisco switch and needs to ensure that only the MAC address 00:1A:2B:3C:4D:5E is allowed to send traffic on interface GigabitEthernet0/1. The administrator also wants the interface to automatically shut down if a different MAC address is detected. Which command sequence should be used?

Accepted Answer

switchport port-security
switchport port-security maximum 1
switchport port-security mac-address 00:1A:2B:3C:4D:5E
switchport port-security violation shutdown. The correct configuration enables port security on the interface, explicitly limits the number of allowed MAC addresses to one, statically assigns the permitted MAC address, and configures the violation action to shut down the port. This ensures that only the designated device can communicate, and any other MAC triggers a shutdown. The explicit maximum command removes ambiguity, and the static MAC entry binds the address to the port.

Answer

switchport port-security
switchport port-security mac-address 00:1A:2B:3C:4D:5E
switchport port-security violation shutdown

Answer

switchport port-security
switchport port-security mac-address sticky 00:1A:2B:3C:4D:5E
switchport port-security violation restrict

Answer

switchport port-security
switchport port-security maximum 2
switchport port-security mac-address 00:1A:2B:3C:4D:5E
switchport port-security violation shutdown

Question 9

A network administrator needs to connect a workstation to a Cisco switch. Which cabling standard and medium should be utilized to ensure full-duplex communication while preventing collision domains?

Accepted Answer

Category 6 twisted-pair cable with full-duplex settings. Category 6 twisted-pair cable with full-duplex settings is the correct combination because modern Ethernet switches support full-duplex on twisted-pair, which eliminates collisions by providing separate transmit and receive paths on different wire pairs. Cat 6 supports gigabit speeds at 100 meters and is the appropriate medium for a workstation-to-switch connection. Full-duplex operation removes the collision domain entirely on that link.

Answer

Coaxial cable with half-duplex settings

Answer

Fiber optic cable with half-duplex settings

Answer

Category 3 twisted-pair cable with full-duplex settings

Question 10

Which device is primarily responsible for managing traffic between different IP subnets in a corporate network?

Accepted Answer

Router. A router operates at Layer 3 (Network layer) and is responsible for forwarding packets between different IP subnets by examining IP addresses and making routing decisions. It maintains a routing table and uses protocols like OSPF or BGP to determine the best path. This makes it the primary device for inter-subnet traffic management in a corporate network.

Answer

Layer 2 Switch

Answer

Hub

Answer

Repeater

Question 11

Which TWO functions are performed by a Cisco switch at the Data Link layer? (Choose two.)

Accepted Answer

Forwarding frames based on destination MAC addresses. Option B is correct because a Cisco switch operates at Layer 2 and forwards frames by looking up the destination MAC address in its MAC address table to select the correct egress port. Option C is correct because the switch learns source MAC addresses from the ingress frames it receives and records them along with the receiving port in its MAC address table, which builds the basis for future forwarding decisions. Option A is incorrect because best-path calculation based on IP addresses is a Layer 3 routing function performed by routers, not switches. Option D is incorrect because translating between different network topologies is not a standard Data Link layer switch function; such translation is typically handled by gateways or specific translation devices. Option E is incorrect because encapsulating data packets into segments is a Layer 4 (Transport layer) function, such as TCP or UDP segmentation, not a switch operation.

Answer

Calculating the best path based on IP addresses

Answer

Translating between different network topologies

Answer

Encapsulating data packets into segments

Question 12

Which THREE factors influence the selection of a specific router interface for traffic forwarding? (Choose three.)

Accepted Answer

Longest prefix match. The router selects a forwarding interface through a two-stage process: first it narrows candidate routes using the longest prefix match (Option A), so the route with the most specific matching network prefix wins over less specific ones. If multiple routes to the same destination prefix are learned from different sources, administrative distance (Option C) breaks the tie by preferring the more trustworthy source (e.g., connected, static, or a given routing protocol). Among routes from the same source/protocol, the metric value (Option D) is compared, and the lowest metric determines the best path and thus the egress interface. The source MAC address (Option B) is a Layer 2 field used for frame delivery and MAC address-table lookups, not for choosing a route or egress interface. The switching fabric capacity (Option E) is an internal hardware throughput characteristic of the device and does not participate in route or interface selection.

Answer

Source MAC address

Answer

Switching fabric capacity

Question 13

An administrator wants to implement a security policy that prevents unauthorized devices from accessing the network via open switch ports. Which feature should be enabled to achieve this?

Accepted Answer

Port Security. Port security is a critical Layer 2 feature that limits the number of MAC addresses allowed on a port or binds specific MAC addresses to a port. This prevents MAC flooding attacks and ensures that only authorized hardware can connect to the infrastructure. By enforcing these policies at the access layer, administrators significantly reduce the risk of unauthorized lateral movement within the network.

Answer

VLAN Trunking Protocol

Answer

Spanning Tree Protocol

Answer

Dynamic ARP Inspection

Question 14

Which primary benefit does the implementation of VLANs provide to a corporate network infrastructure?

Accepted Answer

Reduction of broadcast domain size. VLANs divide a single physical switch into multiple logical broadcast domains. This segmentation reduces the size of broadcast domains, which minimizes unnecessary traffic processing on end devices and improves overall network stability. By grouping devices logically rather than physically, administrators gain greater control over resource access and improve security by isolating traffic between different departments or functional roles.

Answer

Increased physical cabling requirements

Answer

Automatic encryption of all traffic

Answer

Elimination of the need for routers

Question 15

Which transmission medium is best suited for long-distance data communication with high immunity to electromagnetic interference?

Accepted Answer

Fiber Optic Cable. Fiber optic cable is the best choice for long-distance data communication with high immunity to electromagnetic interference (EMI) because it transmits data as pulses of light through a glass or plastic core rather than electrical signals. Since light is unaffected by electromagnetic fields, fiber is completely immune to EMI and radio frequency interference (RFI). Additionally, fiber has much lower attenuation than copper, allowing signals to travel many kilometers without repeaters, making it ideal for long-haul networks.

Answer

Shielded Twisted Pair (STP)

Answer

Unshielded Twisted Pair (UTP)

Answer

Coaxial Cable