100-150 Practice Test 13 — 15 Questions

Question 1

A network administrator is subnetting the 172.16.0.0/22 network into smaller subnets to support point-to-point WAN links between routers. Each WAN link requires exactly two usable IP addresses. Which subnet mask should the administrator use to maximize the number of subnets while meeting the requirement?

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

Accepted Answer

255.255.255.252. For point-to-point WAN links requiring exactly two usable IP addresses, a /30 subnet mask (255.255.255.252) is the standard choice. It provides two usable addresses and minimizes address waste. While /31 can also work on supported devices, /30 is universally compatible and is the most common recommendation in Cisco curricula.

Answer

255.255.255.240

Answer

255.255.255.254

Answer

255.255.255.248

Question 2

A technician is documenting a small office network that uses a single 48-port Cisco switch. Users complain that when two computers transmit simultaneously, the whole network slows down. The technician confirms the switch is not configured with VLANs and all ports are in the default VLAN. Which characteristic of the default VLAN on a Cisco switch explains this behavior?

Accepted Answer

All switch ports are assigned to VLAN 1 by default, so all devices share the same broadcast domain and are subject to broadcast traffic.. By default, all ports on a Cisco switch belong to VLAN 1, creating one broadcast domain. When many hosts share that domain, broadcast and unknown unicast frames are flooded to every port, which can degrade performance. Separating devices into multiple VLANs reduces broadcast scope and improves overall throughput without requiring new hardware.

Answer

The default VLAN uses a different encapsulation type (ISL) that fragments frames larger than 1500 bytes, increasing overhead.

Answer

VLAN 1 is reserved for management traffic only, so user data is automatically redirected to a separate data VLAN, causing congestion.

Answer

Because VLAN 1 is the native VLAN, it cannot carry IPv4 traffic, and packets are dropped, forcing retransmissions that slow the network.

Question 3

A network administrator is documenting the addressing scheme for a new subnet. The subnet uses the IPv4 address 192.168.100.0 with a prefix length of /26. How many usable host addresses are available in this subnet?

Accepted Answer

62. A /26 subnet mask provides 6 host bits, resulting in 2^6 = 64 total addresses. After reserving the network address and the broadcast address, 62 addresses remain for host assignment. This is a fundamental subnetting calculation that every network technician must master.

Answer

126

Answer

30

Answer

64

Question 4

A network engineer is planning an IPv4 addressing scheme for a point-to-point WAN link between two routers. The engineer wants to conserve addresses and use a mask that provides exactly two usable host addresses on the link. Which subnet mask should be used?

Accepted Answer

255.255.255.252. A /30 subnet mask provides exactly two usable host addresses, which is ideal for point-to-point WAN links. It reserves one address for the network and one for broadcast, leaving the two needed for the router interfaces. Larger subnets waste addresses, and a /32 does not support two hosts.

Answer

255.255.255.224

Answer

255.255.255.255

Answer

255.255.255.248

Question 5

A support technician is configuring a wireless access point for a small office. The office wants to allow guest devices to connect without exposing internal resources, while keeping employee traffic separated. Which feature should the technician configure on the access point?

Accepted Answer

Multiple SSIDs mapped to separate VLANs. Mapping separate SSIDs to distinct VLANs provides logical separation between guest and employee traffic. The access point tags frames with the appropriate VLAN, and the wired network enforces policy between them. MAC filtering, SSID hiding, and shared-key encryption do not create separate network segments.

Answer

MAC address filtering

Answer

WPA2-Personal with a shared passphrase

Answer

SSID broadcast suppression

Question 6

A user on VLAN 20 reports that they cannot reach a server on VLAN 30, but they can reach other devices on VLAN 20 and the Internet. The network uses a Layer 3 switch for inter-VLAN routing. The technician verifies that the user's PC has the correct IP address, subnet mask, and default gateway. Which command should the technician run on the Layer 3 switch to verify that inter-VLAN routing is enabled and functioning?

Accepted Answer

show ip route. The show ip route command reveals the routing table, which on a Layer 3 switch includes directly connected routes for each configured SVI. If inter-VLAN routing is active, the route for the server's VLAN subnet should be present as directly connected. Absence of that route would point to a missing or misconfigured SVI, explaining the connectivity failure.

Answer

show vlan brief

Answer

show interfaces trunk

Answer

show mac address-table

Question 7

A network technician is reviewing a Cisco switch configuration and sees that PortFast and BPDU Guard are enabled on an access port that connects to a user's desktop. The user calls and reports that they accidentally plugged a small unmanaged switch into that wall jack so they could connect both a PC and a printer. Shortly afterward, the port stopped forwarding traffic. What is the most likely explanation for this behavior?

Accepted Answer

The unmanaged switch sent BPDUs that were received on the PortFast port, and BPDU Guard placed the port into the err-disabled state.. When PortFast is enabled on an access port, it allows the port to transition immediately to the forwarding state, bypassing the listening and learning states. To prevent loops, BPDU Guard is often enabled alongside PortFast. If a BPDU is received on a PortFast-enabled port, BPDU Guard err-disables the port. In this scenario, connecting an unmanaged switch causes BPDUs to be sent, triggering BPDU Guard and disabling the port.

Answer

The switch detected a MAC address flapping condition and applied a default port security violation.

Answer

The unmanaged switch negotiated a speed of 10 Mbps, which is unsupported on the access port.

Answer

The unmanaged switch caused a duplex mismatch, and the port was automatically disabled by the switch fabric.

Question 8

A technician is troubleshooting a workstation that cannot connect to the network. The workstation has a link light, but ipconfig shows an IP address of 169.254.10.20. The technician suspects a DHCP-related issue. Which two commands should the technician use to attempt to obtain a new IP address from the DHCP server? (Choose two.)

Accepted Answer

ipconfig /release. An IP address in the 169.254.x.x range indicates that the workstation failed to obtain a lease from a DHCP server and self-assigned an APIPA address. To resolve this, the technician should first release the current APIPA address using ipconfig /release, then request a new lease with ipconfig /renew. These two commands together attempt to re-establish DHCP communication and obtain a valid IP configuration.

Answer

ipconfig /flushdns

Answer

ipconfig /displaydns

Answer

netstat -a

Question 9

A technician is deploying an IP phone in a small branch office and needs to ensure both voice traffic and the phone's power are delivered over a single Ethernet cable. Which IEEE standard should the technician verify the switch port supports?

Accepted Answer

802.3af. Power over Ethernet lets a single cable carry both data and DC power, eliminating the need for a separate power adapter at the desk. The IEEE 802.3af standard is the baseline PoE specification that supplies enough wattage for standard IP phones and similar low-power endpoints, making it the correct standard to confirm on the switch port.

Answer

802.11ac

Answer

802.1Q

Answer

802.3ad

Question 10

A user calls the help desk and reports that a laptop cannot reach any websites or internal servers. The technician runs ipconfig and sees that the laptop has an IPv4 address of 169.254.88.12 with a subnet mask of 255.255.0.0 and no default gateway. Which action should the technician take FIRST to resolve the problem?

Accepted Answer

Check the physical Ethernet cable and the switch port link status for the laptop.. An address in the 169.254.0.0/16 range is assigned automatically by the operating system when DHCP attempts fail, so the laptop never obtained a valid lease. The most likely causes are a disconnected or faulty cable, a disabled switch port, or a VLAN mismatch. Confirming the physical link and the switch port status is the fastest, least disruptive first step before changing any server or client configuration.

Answer

Restart the DHCP service on the Windows server that serves the user's subnet.

Answer

Configure a static IP address, subnet mask, and default gateway on the laptop.

Answer

Clear the DNS resolver cache on the laptop with ipconfig /flushdns.

Question 11

A network administrator is setting up a small office network with a Cisco router and several switches. The administrator wants to ensure that devices on the local network can communicate with each other and access the internet. Which IP address configuration parameter must be set on each device to allow communication with remote networks?

Accepted Answer

Default gateway. The default gateway is the router's IP address on the local subnet that devices use to forward packets destined for remote networks. Without it, a device can only communicate locally. The subnet mask helps identify local versus remote destinations, but the default gateway provides the actual path to those remote networks.

Answer

MAC address

Answer

DNS server

Answer

Subnet mask

Question 12

A network administrator is connecting two switches directly using a copper cable. Both switches are modern and support auto-MDI/MDIX. Which cable type is required for this connection?

Accepted Answer

A straight-through cable. Auto-MDI/MDIX eliminates the need to choose between straight-through and crossover copper cables for device-to-device links. When both switches support this feature, a standard straight-through cable is sufficient because the ports negotiate the correct transmit and receive pairing automatically. Crossover cabling is only mandatory when auto-detection is absent on at least one side.

Answer

A rollover cable

Answer

A fiber-optic patch cord

Answer

A crossover cable

Question 13

A network technician connects a new Cisco Catalyst switch to an existing production switch using a copper straight-through cable. The link lights on both ends remain off, and the technician confirms the cable is functional. The technician then replaces the cable with a crossover cable, and the link comes up. What is the most likely reason the straight-through cable failed to establish a link?

Accepted Answer

The new switch does not support Auto-MDIX, and both devices use the same pinout for transmit and receive pairs.. Two switches connected with a straight-through cable without Auto-MDIX will not establish a link because transmit and receive pairs are not crossed. A crossover cable swaps the pairs, allowing the link to come up. The scenario confirms the cable itself is functional, so the issue is the pinout mismatch between similar devices.

Answer

The straight-through cable is wired to T568A on one end and T568B on the other.

Answer

The switch port on the existing production switch is configured as a trunk port.

Answer

The existing production switch port is shut down administratively.

Question 14

A technician is troubleshooting a workstation that cannot reach any network resources. The workstation's IP configuration shows an address of 169.254.10.22 and a subnet mask of 255.255.0.0. Which condition does this indicate?

Accepted Answer

The workstation is using an APIPA address because it could not contact a DHCP server.. The 169.254.0.0/16 address range is reserved for APIPA, which a host self-assigns when its DHCP discover broadcasts receive no response. This means the workstation has no valid IP, gateway, or DNS information, explaining why all network resources are unreachable. The correct diagnosis is a DHCP communication failure, not a configuration conflict or gateway error.

Answer

The workstation successfully received an IP address from a DHCP server.

Answer

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

Answer

The workstation is configured with an incorrect default gateway.

Question 15

A technician is troubleshooting a user's workstation that cannot reach any resources on a remote subnet, though local subnet communication works fine. The technician suspects a routing or default gateway issue. Which command should be used on the workstation to verify the configured default gateway address?

Accepted Answer

ipconfig /all. When a workstation can communicate on the local subnet but fails to reach remote networks, the default gateway configuration is a primary suspect. The ipconfig /all command on Windows provides a comprehensive view of the IP configuration, including the default gateway address, allowing the technician to confirm whether it is correctly set or missing.

Answer

ping localhost

Answer

netstat -r

Answer

nslookup