100-150 Standards and Concepts Practice Test 2 — 15 Questions

Question 1

Which field in an IPv4 header is used to prevent a packet from circulating indefinitely in the event of a routing loop?

Accepted Answer

Time to Live (TTL). The Time to Live (TTL) field in the IPv4 header is an 8-bit value that is decremented by one at each router hop. When it reaches zero, the router discards the packet and sends an ICMP Time Exceeded message back to the source, preventing packets from looping forever in the event of a routing loop.

Answer

Protocol Field

Answer

Header Checksum

Answer

Differentiated Services (DiffServ)

Question 2

A user is unable to reach 'cisco.com' in their web browser but can successfully ping the IP address '72.163.4.161'. Which network service is most likely failing or misconfigured?

Accepted Answer

Domain Name System (DNS). This scenario highlights the distinction between basic connectivity and name resolution. If a user can reach a destination by IP but not by name, the underlying network path is functional, but the translation service is broken. Diagnosing DNS issues is a daily task for technicians, as it is often the root cause of 'internet is down' complaints when the connection is actually active.

Answer

Dynamic Host Configuration Protocol (DHCP)

Answer

Network Address Translation (NAT)

Answer

Address Resolution Protocol (ARP)

Question 3

A network administrator is troubleshooting an issue where a workstation cannot communicate with a server on a different subnet. The workstation has an IP address of 192.168.1.5/24 and the server is at 192.168.2.10/24. Which component is strictly responsible for routing traffic across these disparate subnets?

Accepted Answer

The router or Layer 3 gateway. Routing traffic between distinct subnets requires a Layer 3 device capable of making forwarding decisions based on destination IP addresses. While switches operate at Layer 2 for local segments, they cannot bridge traffic across different broadcast domains without an inter-VLAN routing interface or a dedicated router. Understanding this boundary is fundamental to network architecture and ensuring proper traffic flow in multi-segment environments.

Answer

The local Layer 2 switch

Answer

The network interface card (NIC)

Answer

The ARP cache on the workstation

Question 4

Which TWO of the following statements accurately describe the characteristics of the OSI model's Data Link layer (Layer 2)? (Choose two.)

Accepted Answer

It handles physical addressing via MAC addresses.. Option B is correct because the Data Link layer (Layer 2) is responsible for physical addressing using MAC addresses, which are burned into network interface cards and used to deliver frames on the local segment. Option D is correct because the IEEE 802 model divides Layer 2 into two sublayers: the Logical Link Control (LLC) sublayer, which handles framing and flow control, and the Media Access Control (MAC) sublayer, which governs access to the shared physical medium. Option A is incorrect because logical addressing via IP headers is a function of the Network layer (Layer 3), not Layer 2. Option C is incorrect because end-to-end delivery across multiple routers is a transport-layer (Layer 4) responsibility, while Layer 2 only handles node-to-node delivery on the same link. Option E is incorrect because path determination and routing are performed by Layer 3 routing protocols, not by the Data Link layer.

Answer

It provides logical addressing through IP protocol headers.

Answer

It manages end-to-end data delivery across multiple routers.

Answer

It determines the best path to reach a remote destination.

Question 5

Refer to the exhibit. An administrator observes that interface Gig0/1 is in 'up' status but experiences high latency and interface errors. Based on the provided configuration, what is the most likely cause?

Accepted Answer

The interface is set to auto-negotiate, causing a duplex mismatch.. An interface that is 'up' but shows high latency and errors typically indicates a duplex mismatch, which occurs when one side is hard-set to full duplex and the other auto-negotiates to half duplex. This causes collisions, late collisions, FCS errors, and degraded throughput. The exhibit's configuration showing auto-negotiation on one side and a fixed setting on the other confirms this scenario.

Answer

The cable is faulty.

Answer

The interface is administratively shut down.

Answer

The bandwidth is too low for traffic.

Question 6

Which protocol operates at the Application layer of the TCP/IP model and is used to resolve hostnames into IP addresses?

Accepted Answer

DNS. DNS (Domain Name System) operates at the Application layer of the TCP/IP model and is responsible for resolving human-readable hostnames (like www.example.com) into IP addresses. It uses UDP port 53 for standard queries and TCP port 53 for zone transfers and large responses.

Answer

DHCP

Answer

ARP

Answer

HTTP

Question 7

Which THREE features are provided by the Transport layer of the OSI model? (Choose three.)

Accepted Answer

Flow control. Option A (Flow control) is correct because the Transport layer manages end-to-end flow control, using mechanisms like windowing in TCP to prevent a fast sender from overwhelming a slow receiver. Option C (Segmentation and reassembly) is correct because the Transport layer breaks application data into segments at the sender and reassembles them in the correct order at the destination, using sequence numbers. Option D (Error recovery) is correct because the Transport layer detects lost, corrupted, or out-of-order segments and retransmits them (e.g., TCP acknowledgments and retransmission timers) to provide reliable delivery. Option B (Physical addressing) does not belong because physical (MAC) addressing is handled by the Data Link layer. Option E (Path selection) does not belong because routing and path selection are functions of the Network layer.

Answer

Physical addressing

Answer

Path selection

Question 8

A network administrator needs to ensure that data remains confidential during transit across an untrusted network. Which protocol implementation best addresses this requirement?

Accepted Answer

SSH. SSH (Secure Shell) provides encrypted, authenticated communication over untrusted networks, typically on TCP port 22, using strong cryptographic algorithms to protect data in transit. It replaces insecure remote-access protocols like Telnet by encrypting the entire session, ensuring confidentiality and integrity. This directly satisfies the requirement that data remain confidential during transit.

Answer

Telnet

Answer

HTTP

Answer

SNMPv1

Question 9

Which of the following scenarios best demonstrates the function of the Network layer in the OSI model?

Accepted Answer

A router determining the best path to reach a remote subnet.. The Network layer is responsible for logical addressing and routing. When data must travel between different networks, the Network layer determines the optimal path using routing protocols and IP addressing. This is critical for global network connectivity, as it allows packets to traverse multiple routers and hop between disparate subnetworks to reach their final destination across the internet or enterprise infrastructure.

Answer

A switch forwarding a frame based on a destination MAC address.

Answer

A client establishing a TCP three-way handshake with a server.

Answer

A browser displaying an HTML page retrieved from a web server.

Question 10

Which field in the IPv4 header is primarily responsible for preventing a packet from looping indefinitely in a network?

Accepted Answer

Time-to-Live (TTL). The Time-to-Live (TTL) field in the IPv4 header is an 8-bit value that is decremented by one each time a packet passes through a router. When TTL reaches zero, the router discards the packet and sends an ICMP Time Exceeded message back to the source. This mechanism prevents packets from looping indefinitely due to routing loops or misconfigurations.

Answer

Protocol

Answer

Fragment Offset

Answer

Header Checksum

Question 11

Which of the following best describes the benefit of implementing a hierarchical network design model?

Accepted Answer

It simplifies network management and promotes scalability.. Hierarchical designs, such as the Cisco Core-Distribution-Access model, improve scalability, performance, and manageability. By separating functions into layers, administrators can apply policies and scale specific parts of the network without impacting the entire infrastructure. This modularity is essential for modern enterprise networks that require high availability and consistent performance across thousands of connected devices and diverse geographic locations.

Answer

It eliminates the need for routing protocols.

Answer

It forces all traffic to be processed by a single core router.

Answer

It ensures that all devices operate at the same speed.

Question 12

Refer to the exhibit. An administrator is troubleshooting interface Gig0/1. The status is 'up/down'. What is the most likely reason for this state?

Accepted Answer

There is a Layer 2 encapsulation mismatch.. An 'up/down' status typically indicates a Layer 2 issue where the physical link is active but the data link layer is not negotiating correctly. Common causes include encapsulation mismatches, speed/duplex errors, or a failure in the keepalive mechanism. Identifying this specific state helps technicians isolate problems to the Layer 2 domain, preventing unnecessary troubleshooting of Layer 3 IP configurations.

Answer

The cable is disconnected.

Answer

The IP address is incorrectly configured.

Answer

The router is administratively shut down.

Question 13

Which statement correctly describes the function of a default gateway in a host's TCP/IP configuration?

Accepted Answer

It is the router used to access remote networks.. A default gateway is the router interface on the local subnet that a host sends packets to when the destination IP is not on the same local network. Without it, a host can only communicate with devices on its own subnet. The gateway performs Layer 3 routing to forward traffic toward remote networks.

Answer

It resolves domain names into IP addresses.

Answer

It assigns IP addresses to devices on the network.

Answer

It manages data link layer frame switching.

Question 14

When a router receives a packet, what action does it take if the destination network is not in its routing table and no default route is configured?

Accepted Answer

It drops the packet and sends an ICMP error message.. Routers operate based on explicit routing entries. If a destination network is missing and no default gateway (quad-zero route) exists, the router has no path information to forward the packet. It then drops the packet and sends an ICMP 'Destination Unreachable' message back to the sender. This is a vital diagnostic mechanism that informs hosts of connectivity failures.

Answer

It forwards the packet to all connected ports.

Answer

It stores the packet until a route is learned.

Answer

It sends a request to the DNS server for the path.

Question 15

Which of the following describes the purpose of a Subnet Mask in an IP configuration?

Accepted Answer

It identifies the network and host portions of the IP address.. A subnet mask is a 32-bit number that, when combined with an IP address via a bitwise AND operation, reveals the network portion of the address. The remaining bits identify the host portion, enabling devices to determine whether a destination is local or remote.

Answer

It assigns a unique identity to the NIC hardware.

Answer

It increases the transmission speed of the interface.

Answer

It encrypts data packets before transmission.