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Networking Concepts

538 questions

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Question 201Question →

A user pairs a wireless Bluetooth headset directly with a smartphone to listen to audio while working at a desk. Which of the following network types best categorizes this personal, short-range wireless connection?

Show answer & explanation

Answer: Personal Area Network (PAN)

Answer

Personal Area Network (PAN)
A Personal Area Network (PAN) is specifically designed for short-range communication among personal devices centered around an individual's immediate workspace.

Step-by-Step Solution

1
Identify the physical scale and communication technology described in the scenario.
The connection uses Bluetooth between personal devices within immediate physical proximity (under 10 meters).
Network types are categorized based on their geographic scope and intended operational coverage.
2
Select the network classification matching personal short-range connections.
Connections focused around a single individual's personal space constitute a Personal Area Network (PAN).
PAN technology (such as Bluetooth or Zigbee) is designed specifically for interconnecting personal devices in close range.

Key Concept

Personal Area Network (PAN) scope and characteristics
Question 202Question →

Match each Layer 2 switching concept on the left with its primary operational characteristic or function on the right.

Click a left item, then click its matching right item

Items

IEEE 802.1Q
Native VLAN
Port Security
Spanning Tree Protocol (STP)

Matches

Show answer & explanation

Answer

IEEE 802.1Q matches with inserting a 4-byte frame header tag for VLAN identification; Native VLAN matches with carrying untagged frame traffic across trunk links; Port Security matches with restricting switchport traffic based on authorized MAC addresses; Spanning Tree Protocol matches with preventing Layer 2 loops by blocking redundant paths.
IEEE 802.1Q defines the 4-byte VLAN tagging standard for trunking; Native VLAN processes untagged frames across trunk links; Port Security restricts switchport access using MAC addresses; and Spanning Tree Protocol blocks redundant ports to avoid network loops.

Step-by-Step Solution

1
Identify the standard protocol used for VLAN trunk tagging.
IEEE 802.1Q defines inserting a 4-byte header tag into Ethernet frames for VLAN identification across switches.
Trunk links must distinguish frame traffic belonging to different VLAN IDs.
2
Determine how untagged frames are handled across trunk links.
The Native VLAN is designated on 802.1Q trunks to pass untagged frames.
This allows untagged control traffic and legacy frame types to transit trunk connections.
3
Identify the feature that controls port access via physical MAC addresses.
Port Security inspects incoming frames and permits only allowed MAC addresses based on defined limits.
Prevents unauthorized host connection and rogue switch addition at the access layer.
4
Determine the Layer 2 protocol responsible for loop prevention.
Spanning Tree Protocol (STP) monitors switch links and dynamically blocks redundant paths.
Prevents Layer 2 broadcast storms and MAC table instability.

Key Concept

Switching Concepts and VLAN Trunking Mechanisms
Question 203Question →

An industrial facility operates a legacy control network where every client automation terminal connects via an individual twisted-pair cable directly to a central multiport Ethernet switch. However, the media access control protocol running across the network relies on a token-passing scheme, where frame transmission rights are passed sequentially from workstation to workstation in a continuous deterministic cycle. Which option correctly identifies both the physical and logical topologies of this network architecture?

Show answer & explanation

Answer: Physical Star topology and Logical Ring topology

Answer

Physical Star topology and Logical Ring topology
Physical topology refers to the actual arrangement of physical cabling and central connecting devices (in this case, individual cables running from endpoints to a central switch forming a star). Logical topology refers to the path data takes across the network (in this case, token passing sequentially from node to node in a logical circle). Therefore, the deployment is a Physical Star, Logical Ring topology.

Step-by-Step Solution

1
Analyze the physical layout description.
Individual point-to-point cables running from each endpoint directly into a central multiport switch define a Physical Star layout.
Physical topology represents the actual physical cabling and hardware layout of the network infrastructure.
2
Analyze the data transmission mechanism.
Sequentially passing token rights from node to node in a deterministic cycle defines a Logical Ring topology.
Logical topology describes how data actually travels across the network protocol stack regardless of the underlying physical cable routes.
3
Synthesize the physical and logical characteristics.
The infrastructure combines a Physical Star with a Logical Ring.
Matching both physical cabling patterns and logical frame flow paths confirms the hybrid topology classification.

Key Concept

Distinction between Physical Topology (hardware deployment) and Logical Topology (data path/access control)
Estimated Time:2m 0s
Question 204Question →

A network router receives route advertisements for the same destination network from two different dynamic routing protocols: OSPF and RIP. The router automatically prefers the route learned through OSPF over the route learned through RIP. Which criterion does the router use first to compare the trustworthiness of these different routing protocols?

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Answer: Administrative distance

Answer

Administrative distance is used by routers to evaluate the trustworthiness of routes learned via different routing sources.
Administrative distance (AD) is a rating of trustworthiness of a routing information source on a scale from 0 to 255. A lower value signifies a more reliable protocol. Since OSPF has a lower administrative distance (110) than RIP (120), the router prefers the OSPF path.

Step-by-Step Solution

1
Identify the scenario requirement
The router has two routes to the same network from different sources (OSPF and RIP).
When multiple routes to a single network are learned via different protocols, the router must decide which source is more trustworthy.
2
Evaluate protocol preference metric
Administrative distance (AD) is evaluated first.
AD defines trustworthiness; lower AD values mean higher believability (OSPF AD = 110, RIP AD = 120).

Key Concept

Administrative Distance in Dynamic Routing
Question 205Question →

A network administrator is assigned the IPv4 address block 172.28.64.0/21172.28.64.0/21 to provision subnets for a multi-department enterprise deployment. Using Variable Length Subnet Masking (VLSM), subnets must be allocated sequentially starting from the lowest available IP address in order of capacity requirements (from largest to smallest):

- Subnet A: Requires capacity for up to 400400 usable host IP addresses.
- Subnet B: Requires capacity for up to 180180 usable host IP addresses.
- Subnet C: Requires capacity for up to 6060 usable host IP addresses.
- Subnet D: Requires capacity for exactly 22 usable host IP addresses.

Each subnet must be allocated using the smallest valid CIDR prefix length that accommodates its requirement. What is the total number of unallocated IP addresses remaining in the 172.28.64.0/21172.28.64.0/21 block after all four subnets are allocated?

Show answer & explanation

Answer: 1212

Answer

The total number of unallocated IP addresses remaining in the 172.28.64.0/21172.28.64.0/21 parent block after provisioning all four subnets is 1212.
The parent block 172.28.64.0/21172.28.64.0/21 contains 20482048 total IP addresses. Allocating the subnets sequentially requires: Subnet A (400400 hosts) →/23\rightarrow /23 (512512 IPs), Subnet B (180180 hosts) →/24\rightarrow /24 (256256 IPs), Subnet C (6060 hosts) →/26\rightarrow /26 (6464 IPs), and Subnet D (22 hosts) →/30\rightarrow /30 (44 IPs). Total allocated IP space is 512+256+64+4=836512 + 256 + 64 + 4 = 836 IP addresses. Subtracting 836836 from 20482048 leaves 12121212 total unallocated IP addresses.

Step-by-Step Solution

1
Calculate total IP address capacity of the parent block
172.28.64.0/21172.28.64.0/21 contains 232−21=211=20482^{32-21} = 2^{11} = 2048 total IP addresses
A /21/21 prefix uses 21 network bits, leaving 11 host bits for addressing.
2
Determine prefix length and block size for Subnet A
Prefix: /23/23, Block size: 512512 total IPs (172.28.64.0/23172.28.64.0/23)
To support 400400 hosts, 9 host bits are needed (29−2=510≥4002^9 - 2 = 510 \ge 400), giving a /23/23 prefix (512512 IPs).
3
Determine prefix length and block size for Subnet B
Prefix: /24/24, Block size: 256256 total IPs (172.28.66.0/24172.28.66.0/24)
To support 180180 hosts, 8 host bits are needed (28−2=254≥1802^8 - 2 = 254 \ge 180), giving a /24/24 prefix (256256 IPs).
4
Determine prefix length and block size for Subnet C
Prefix: /26/26, Block size: 6464 total IPs (172.28.67.0/26172.28.67.0/26)
To support 6060 hosts, 6 host bits are needed (26−2=62≥602^6 - 2 = 62 \ge 60), giving a /26/26 prefix (6464 IPs).
5
Determine prefix length and block size for Subnet D
Prefix: /30/30, Block size: 44 total IPs (172.28.67.64/30172.28.67.64/30)
To support 22 hosts (point-to-point link), 2 host bits are needed (22−2=2≥22^2 - 2 = 2 \ge 2), giving a /30/30 prefix (44 IPs).
6
Calculate remaining unallocated IP space
2048−(512+256+64+4)=2048−836=12122048 - (512 + 256 + 64 + 4) = 2048 - 836 = 1212 IP addresses
Subtracting the sum of all allocated CIDR block sizes from the total parent address space yields the remaining unallocated IP addresses.

Key Concept

Variable Length Subnet Masking (VLSM) allocation and host requirement calculations
Question 206Question →

Which IP addressing service is specifically designed to synchronize clock settings across network devices to maintain consistent timestamps in system logs?

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Answer: Network Time Protocol (NTP)

Answer

Network Time Protocol (NTP) is the service used to synchronize time settings across network hosts.
The Network Time Protocol (NTP) synchronizes computer clock times across a network to ensure that event logs, kerberos authentication, and scheduled tasks remain aligned accurately.

Step-by-Step Solution

1
Identify the service required for clock synchronization
Network Time Protocol (NTP) provides network-wide time synchronization.
NTP operates over UDP port 123 to ensure all system clocks agree across enterprise network infrastructure.

Key Concept

Network Time Protocol (NTP) Functionality
Question 207Question →

A small business owner is setting up a local network in a new office space. Every desktop computer in the office connects directly to a central Ethernet switch using an individual network cable. Which physical network topology does this deployment represent?

Show answer & explanation

Answer: Star topology

Answer

Star topology
The star topology is characterized by connecting all individual network nodes back to a single central connecting device, such as a network switch or hub. If a single endpoint cable fails, only that device is disconnected from the network.

Step-by-Step Solution

1
Analyze the physical connectivity described in the scenario
Identified that each host device connects independently to a central Ethernet switch
Determining node-to-central-device connectivity points directly to physical layout characteristics
2
Match the layout characteristics to standard physical network topologies
A central connectivity hub with point-to-point host runs is defined as a star topology
Star topology is defined by all endpoints connecting individually to a central distribution device like a switch or hub

Key Concept

Physical Star Topology
Question 208Question →

A network technician analyzing a packet capture notes that after a reliable TCP connection is established, the client and server begin negotiating TLS encryption algorithms and encoding character sets for data formatting. At which layer of the OSI model does this data encryption and formatting negotiation take place?

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Answer: Presentation Layer (Layer 6)

Answer

The Presentation Layer (Layer 6) handles data formatting, character encoding, and cryptographic negotiation such as TLS.
The Presentation Layer (Layer 6) serves as the environment where data formatting, syntax translation, compression, and encryption standard negotiations (such as TLS/SSL) occur before payload processing.

Step-by-Step Solution

1
Analyze the functions mentioned in the scenario.
The scenario highlights TLS encryption negotiation and character set encoding following the TCP handshake.
Identifying the specific network operations allows mapping them to the proper OSI layer.
2
Map the identified functions to OSI model responsibilities.
Data formatting, translation, compression, and encryption/decryption operate strictly at Layer 6.
Layer 6 (Presentation) ensures data is presented in a readable format and secure state before reaching user applications.

Key Concept

OSI Layer 6 (Presentation Layer) functions
Question 209Question →

A systems administrator is configuring a host-based firewall on a Linux management server. The server must accept incoming secure remote command-line administration sessions using Secure Shell (SSH). Which of the following port and transport protocol combinations must be permitted?

Show answer & explanation

Answer: TCP port 22

Answer

TCP port 22
Secure Shell (SSH) is a secure, encrypted protocol for remote terminal connections that operates by default over TCP port 22.

Step-by-Step Solution

1
Identify the service protocol requested
The scenario specifies Secure Shell (SSH) for secure command-line administration.
Determining the target protocol establishes the baseline default port number requirement.
2
Determine the default port number for SSH
SSH defaults to port 22.
Standard well-known port allocations assign port 22 to SSH and port 23 to Telnet.
3
Determine the transport layer protocol requirement
SSH uses TCP.
Interactive management sessions require reliable, connection-oriented data transfer provided by TCP.

Key Concept

Default Port and Transport Protocol for SSH
Estimated Time:45s
Question 210Question →

A network security administrator is troubleshooting authentication failures for remote client devices connecting to internal corporate resources over a VPN. While directory browsing and LDAP user lookups function normally, domain authentication requests to the Key Distribution Center (KDC) fail whenever kerberos ticket sizes exceed the standard maximum transmission unit (MTU) or fall back to connection-oriented transport. Inspection of the perimeter firewall logs shows blocked traffic destined for the domain controller. Which port and transport protocol combination must be permitted on the firewall to allow complete Kerberos authentication traffic?

Show answer & explanation

Answer: TCP and UDP port 88

Answer

Permitting TCP and UDP port 88 on the firewall is required for full Kerberos authentication functionality.
Kerberos authentication services (KDC) operate on port 88 using both TCP and UDP protocols. UDP port 88 handles standard small authentication requests, while TCP port 88 is required when ticket payloads exceed buffer/MTU sizes or require connection-oriented delivery.

Step-by-Step Solution

1
Identify the service protocol responsible for ticket-based domain authentication.
The service is Kerberos, managed by the Key Distribution Center (KDC) on domain controllers.
Kerberos is the primary authentication protocol used in enterprise Active Directory domains.
2
Determine the standard port assignment for Kerberos.
Kerberos utilizes standard port 88.
IANA assigns port 88 to the Kerberos authentication system.
3
Evaluate transport layer requirements for Kerberos.
Kerberos uses UDP port 88 by default for lightweight ticket requests, but automatically falls back to TCP port 88 when authentication tickets exceed packet size thresholds or when connection reliability is required.
Firewalls blocking TCP port 88 cause subtle authentication failures when PAC (Privilege Attribute Certificate) data enlarges Kerberos tickets beyond MTU limits.

Key Concept

Kerberos Port and Transport Protocol Requirements
Question 211Question →

An enterprise network administrator is configuring perimeter firewall rules to isolate an application subnet while enabling secure integration with centralized infrastructure services in the management zone. The application servers require three network communication capabilities:

1. Directory lookup services using StartTLS (explicit TLS negotiation over the standard directory port).
2. Centralized event logging using secure transport (Syslog over TLS according to RFC 5425).
3. Ticket-granting user authentication via Kerberos.

Which combination of transport protocols and destination port numbers must be permitted on the firewall to satisfy all three requirements?

Show answer & explanation

Answer: TCP 389 for LDAP StartTLS, TCP 6514 for Syslog over TLS, and TCP/UDP 88 for Kerberos

Answer

TCP 389 for LDAP StartTLS, TCP 6514 for Syslog over TLS, and TCP/UDP 88 for Kerberos
The option specifying TCP 389 for LDAP StartTLS, TCP 6514 for Syslog over TLS, and TCP/UDP 88 for Kerberos is correct. StartTLS uses explicit TLS negotiation initiating over standard LDAP TCP port 389. Syslog over TLS (RFC 5425) is standardized to use TCP port 6514 for reliable encrypted log transmission. Kerberos authentication uses port 88 over both TCP and UDP.

Step-by-Step Solution

1
Determine the transport port and protocol required for LDAP StartTLS.
LDAP StartTLS begins as cleartext on the standard LDAP port TCP 389 and upgrades to TLS encryption within the session via the STARTTLS extended request. (Implicit LDAPS uses TCP 636).
Explicit TLS protocols initiate on standard unencrypted ports before upgrading, whereas implicit TLS protocols listen on dedicated secure ports.
2
Determine the transport port and protocol required for Syslog over TLS.
Syslog over TLS (RFC 5425) uses TCP port 6514 to ensure reliable delivery and TLS session encryption. Standard unencrypted syslog operates on UDP port 514.
Secure syslog requires connection-oriented TCP to maintain the TLS session and guarantee log packet delivery.
3
Determine the transport ports and protocols required for Kerberos authentication.
Kerberos authentication services operate on destination port 88 using both TCP and UDP.
Kerberos utilizes UDP for lightweight ticket requests and falls back to TCP for larger ticket payloads or TCP-only enforcement.
4
Combine the identified protocol and port requirements.
The correct rule configuration allows TCP 389, TCP 6514, and TCP/UDP 88.
This exact rule set satisfies all three security and functional requirements.

Key Concept

Common Ports and Protocols
Question 212Question →

A network administrator is categorizing application protocols and network workloads based on their transport layer requirements. Match each operational scenario on the left with the corresponding transport protocol characteristic on the right.

Click a left item, then click its matching right item

Items

HTTPS web traffic requiring guaranteed, ordered packet delivery and TLS encryption session tracking
VoIP audio stream where minimal packet delay is critical and lost packets should not be retransmitted
TFTP firmware download utilizing lightweight headers and application-controlled reliability
BGP router peer session exchanging routing table updates over a persistent link

Matches

Show answer & explanation

Answer

HTTPS matches connection-oriented transport with a three-way handshake and sequence numbers; VoIP matches connectionless transport with low-latency overhead; TFTP matches connectionless transport without transport-level session state; and BGP matches connection-oriented reliable byte-stream delivery.
The pairings correctly match application requirements to their underlying Layer 4 protocol mechanisms. TCP provides reliable, ordered, session-based transport for HTTPS and BGP, whereas UDP provides low-overhead, unacknowledged datagram transport for VoIP and TFTP.

Step-by-Step Solution

1
Analyze each application scenario to determine if session state, packet sequencing, and retransmission are required.
HTTPS and BGP require session reliability and ordering (TCP), whereas VoIP and TFTP prioritize low overhead and connectionless behavior (UDP).
Connection-oriented transport manages flow control and guarantees delivery, while connectionless transport provides best-effort delivery without connection setup.
2
Match HTTPS and BGP to their specific TCP transport characteristics.
HTTPS pairs with three-way handshake/sequence number features, while BGP pairs with persistent reliable byte-stream delivery.
Web encryption and dynamic routing table updates cannot tolerate corrupted or missing data.
3
Match VoIP and TFTP to their specific UDP transport characteristics.
VoIP pairs with low-latency unacknowledged transmission, while TFTP pairs with stateless, lightweight transport datagram delivery.
Real-time voice communication drops late packets, and simple file transfer protocols reduce header processing overhead.

Key Concept

Connection-Oriented (TCP) vs Connectionless (UDP) Transport Protocol Operational Characteristics
Question 213Question →

A network architect is assigned the parent block 10.200.16.0/2010.200.16.0/20 to provision subnets for a new regional facility. Using Variable Length Subnet Masking (VLSM), the subnets must be allocated contiguously starting from the lowest available IP address in the block, ordered from the largest host requirement to the smallest. The site requirements are as follows:

- Data Center: minimum 900900 usable host IPs
- Office Floor A: minimum 400400 usable host IPs
- Office Floor B: minimum 100100 usable host IPs

After successfully allocating these three subnets, what is the broadcast address of the subnet allocated to Office Floor B?

Show answer & explanation

Answer: 10.200.22.12710.200.22.127

Answer

The broadcast address of the subnet allocated to Office Floor B is 10.200.22.12710.200.22.127.
Allocating subnets sequentially using VLSM requires allocating block sizes based on power-of-two host requirements. 900 hosts need a /22 (1024 IPs: 10.200.16.0–10.200.19.255). 400 hosts need a /23 (512 IPs: 10.200.20.0–10.200.21.255). 100 hosts need a /25 (128 IPs: 10.200.22.0–10.200.22.127). The broadcast address for Office Floor B's /25 subnet is 10.200.22.127.

Step-by-Step Solution

1
Calculate the required prefix length and range for the Data Center (900 usable hosts).
Requires 1010 host bits (210−2=10222^{10} - 2 = 1022 usable hosts), which corresponds to a /22/22 mask (10241024 total addresses). The subnet range is 10.200.16.0/2210.200.16.0/22, spanning 10.200.16.010.200.16.0 to 10.200.19.25510.200.19.255.
VLSM requires placing the largest subnet first at the start of the block.
2
Calculate the required prefix length and range for Office Floor A (400 usable hosts).
Requires 99 host bits (29−2=5102^9 - 2 = 510 usable hosts), which corresponds to a /23/23 mask (512512 total addresses). Starting at the next available IP (10.200.20.010.200.20.0), the subnet range is 10.200.20.0/2310.200.20.0/23, spanning 10.200.20.010.200.20.0 to 10.200.21.25510.200.21.255.
The subnet must begin immediately after the preceding /22/22 block boundary.
3
Calculate the required prefix length and range for Office Floor B (100 usable hosts).
Requires 77 host bits (27−2=1262^7 - 2 = 126 usable hosts), which corresponds to a /25/25 mask (128128 total addresses). Starting at 10.200.22.010.200.22.0, the subnet range is 10.200.22.0/2510.200.22.0/25, spanning 10.200.22.010.200.22.0 to 10.200.22.12710.200.22.127.
A /25/25 subnet provides 128 total addresses, with the first address (10.200.22.010.200.22.0) as Network ID and the last address (10.200.22.12710.200.22.127) as Broadcast.

Key Concept

Variable Length Subnet Masking (VLSM) Host Capacity Allocation
Question 214Question →

Which TWO of the following statements correctly describe the fundamental operational characteristics of Virtual Local Area Networks (VLANs) and Layer 2 switch traffic processing?

Select all that apply

Show answer & explanation

Answer: Each VLAN configured on a switch defines an isolated Layer 2 broadcast domain.; Trunk links use IEEE 802.1Q encapsulation to append VLAN identification tags to Ethernet frames traversing switches.

Answer

The correct statements are that each VLAN creates an isolated broadcast domain, and trunk links use IEEE 802.1Q encapsulation to tag frames traversing switches.
Configuring separate VLANs logically segments a physical switch into distinct Layer 2 broadcast domains, restricting broadcast traffic within each VLAN. Furthermore, when traffic from multiple VLANs travels across a shared trunk link between network switches, the IEEE 802.1Q protocol adds a tag header to each frame to identify its associated VLAN.

Step-by-Step Solution

1
Analyze the core function of VLAN segmentation on a switch.
Creating a VLAN establishes a separate logical network and broadcast domain on the Layer 2 switch.
This limits broadcast propagation to ports belonging strictly to that specific VLAN.
2
Analyze trunk link operations across multiple switches.
IEEE 802.1Q tagging appends VLAN IDs to frames so recipient switches maintain proper traffic separation.
Trunking allows multiple VLANs to share a single physical link while maintaining individual VLAN isolation.
3
Evaluate distractor claims regarding inter-VLAN routing, forwarding headers, and native VLAN handling.
Inter-VLAN traffic requires Layer 3 routing, Layer 2 switches inspect MAC addresses, and untagged trunk traffic belongs to the native VLAN.
These findings eliminate wrong options related to direct inter-VLAN communication, Layer 3 switching confusion, and dropping untagged frames.

Key Concept

VLAN Broadcast Isolation & IEEE 802.1Q Trunk Tagging
Question 215Question →

A network administrator needs to configure edge firewall rules to allow remote terminal access over an encrypted command-line interface as well as secure web traffic to an internal web server. Which TWO standard protocol and port combinations must be permitted through the firewall?

Select all that apply

Show answer & explanation

Answer: SSH over TCP port 22; HTTPS over TCP port 443

Answer

The firewall rules must permit SSH traffic using TCP port 22 and HTTPS traffic using TCP port 443.
SSH on TCP port 22 meets the requirement for secure command-line administration, while HTTPS on TCP port 443 meets the requirement for encrypted web application access.

Step-by-Step Solution

1
Identify the required secure service for remote command-line access.
SSH provides encrypted shell access using default TCP port 22.
Telnet is unencrypted on TCP port 23, making SSH on TCP port 22 the correct choice.
2
Identify the required secure protocol for web server access.
HTTPS encrypts web communications using default TCP port 443.
Standard HTTP uses unencrypted TCP port 80, whereas HTTPS uses TCP port 443.

Key Concept

Standard default port assignments for secure network management and web services.
Question 216Question →

A network administrator is planning a local network deployment using a physical star topology for a newly opened branch office. Which of the following represent key operational characteristics of a physical star topology? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: All host endpoints connect directly to a central networking device such as a switch.; A failure in an individual host cable run does not cause an outage for other connected devices.

Answer

The correct characteristics are that all host endpoints connect directly to a central networking device such as a switch, and a failure in an individual host cable run does not cause an outage for other connected devices.
In a physical star topology, all network endpoints are connected directly to a central connecting device (such as a Layer 2 switch). This architecture provides host fault isolation, ensuring that a severed cable connected to one host does not affect the connectivity of other hosts on the switch.

Step-by-Step Solution

1
Analyze the physical structure of a star topology.
Identify that devices connect individually to a central distribution point (e.g., a switch).
Centralization is the defining physical property of star architecture.
2
Evaluate fault isolation behavior for star topologies.
Confirm that an open circuit or cable failure on a single endpoint cable only impacts that single endpoint.
Independent point-to-point cable runs prevent single endpoint failures from propagating across the network.

Key Concept

Physical Star Topology Architecture and Fault Isolation
Estimated Time:45s
Question 217Question →

A network host connected to access port FastEthernet0/1 (assigned to VLAN 15) transmits an Ethernet frame intended for a target host. The destination MAC address of this frame is currently absent from the switch's Content Addressable Memory (CAM) table. Port FastEthernet0/2 is an access port in VLAN 15, port FastEthernet0/3 is an access port in VLAN 20, and port GigabitEthernet0/1 is an IEEE 802.1Q trunk port allowing all VLANs. How does the switch handle and forward this unknown unicast frame?

Show answer & explanation

Answer: The switch floods the frame out all active interfaces belonging to VLAN 15 (including FastEthernet0/2 and trunk port GigabitEthernet0/1 with an 802.1Q tag), while excluding the ingress port FastEthernet0/1 and VLAN 20 port FastEthernet0/3.

Answer

The switch floods the frame out all active interfaces assigned to VLAN 15 (including FastEthernet0/2 and trunk port GigabitEthernet0/1 with an 802.1Q tag for VLAN 15), excluding the receiving port FastEthernet0/1 and FastEthernet0/3 in VLAN 20.
When a Layer 2 switch receives an Ethernet frame with a destination MAC address not present in its CAM table, it performs unknown unicast flooding. This operation floods the frame out every active port within the same VLAN except the port on which the frame was received. Furthermore, trunk links carrying that VLAN will receive the frame with an 802.1Q tag attached so the downstream switch maintains proper VLAN identification.

Step-by-Step Solution

1
Analyze the frame type and CAM table status.
The destination MAC address is missing from the switch's MAC address table, making this an 'unknown unicast' frame.
Layer 2 switches forward known unicast frames directly to specific ports, but must flood unknown unicast frames to ensure delivery.
2
Determine the broadcast domain boundaries for the ingress port.
The ingress port FastEthernet0/1 is assigned to VLAN 15.
VLANs define Layer 2 broadcast domain boundaries; flooding is strictly limited to ports associated with the ingress frame's VLAN.
3
Identify valid outgoing egress ports.
FastEthernet0/2 (VLAN 15 access port) and GigabitEthernet0/1 (trunk port allowing VLAN 15) are valid egress ports. FastEthernet0/1 (ingress port) and FastEthernet0/3 (VLAN 20) are excluded.
Split horizon rules prevent sending the frame back out the ingress port, and VLAN segmentation prevents sending frames across VLAN boundaries.
4
Evaluate trunk port tagging behavior.
The frame is tagged with an 802.1Q header containing VLAN ID 15 before being sent across trunk port GigabitEthernet0/1.
Non-native VLAN traffic forwarded across an 802.1Q trunk link must be tagged so the receiving switch can identify its target VLAN.

Key Concept

Layer 2 Unknown Unicast Flooding & VLAN Segmentation
Question 218Question →

A network technician needs to permit direct Server Message Block (SMB) file sharing traffic through an internal firewall between two subnets. Which protocol and default port combination must be allowed?

Show answer & explanation

Answer: TCP port 445

Answer

TCP port 445 must be allowed for direct SMB file sharing.
Server Message Block (SMB) enables direct file sharing over TCP port 445. It relies on TCP to guarantee reliable delivery and ordered sequencing of file data across network subnets.

Step-by-Step Solution

1
Identify the required network service and protocol.
The scenario specifies direct Server Message Block (SMB) file sharing.
SMB is the standard protocol for sharing files and printer resources across IP networks.
2
Determine the transport protocol and default port for direct SMB.
Direct SMB operates using TCP over port 445.
TCP provides reliable, connection-oriented data transfer essential for file operations, and port 445 is the standard IANA port for direct SMB over IP.

Key Concept

Server Message Block (SMB) default port and transport protocol
Question 219Question →

During a network performance audit of a bulk file transfer, an engineer observes that the host systems are negotiating window sizes to manage transmission speed and assigning sequence numbers to reassemble out-of-order data segments. Which layer of the OSI model is responsible for performing these flow control, segmentation, and error-recovery functions?

Show answer & explanation

Answer: Transport Layer

Answer

The Transport Layer is responsible for flow control, segmentation, sequence numbering, and end-to-end error recovery.
The Transport Layer (Layer 4) provides transparent transfer of data between end systems. It breaks upper-layer data into manageable segments, assigns sequence numbers to reassemble segments in order, and implements windowing mechanisms to regulate flow control.

Step-by-Step Solution

1
Identify the operational features described in the scenario
The scenario highlights window size negotiation (flow control) and sequence number assignment for data segment reassembly.
These functions ensure reliable and controlled data delivery across end-to-end host connections.
2
Map these functions to the correct OSI layer model level
The Transport Layer (Layer 4) is specifically designated to perform end-to-end segmentation, sequence tracking, and flow control.
Lower layers handle logical routing and physical framing, while higher layers govern session synchronization and data syntax formatting.

Key Concept

OSI Transport Layer Functions (Segmentation, Flow Control, and Sequence Tracking)
Estimated Time:1m 0s
Question 220Question →

An enterprise network administrator is deploying a centralized Voice over IP (VoIP) telephony solution across multiple remote subnets. While legacy IP desk phones receive their server configuration via DHCP Option 150, newly deployed softphone clients rely on DNS to dynamically discover the hostname, port number (UDP 5060), and priority of the primary Session Initiation Protocol (SIP) server within the internal domain. Which DNS resource record type must be created to support this automated service discovery?

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Answer: SRV record

Answer

The SRV (Service) record is required because it maps a specific service name, transport protocol, and domain to the corresponding target hostname, port number, priority, and weight.
SRV (Service Location) records enable network clients to locate specific services using standardized symbolic names. They explicitly contain fields for priority, weight, port number, and target hostname, allowing applications like SIP softphones to dynamically locate servers on non-standard or standard ports without manual end-user configuration.

Step-by-Step Solution

1
Analyze the technical requirements of the scenario
The application requires dynamic discovery of a service host, port number (UDP 5060), and service protocol (SIP).
Standard host records (A/AAAA) only resolve names to IP addresses without specifying transport layer port numbers.
2
Evaluate DNS record capabilities
SRV records are formatted specifically as `_service._proto.name. TTL CLASS SRV priority weight port target.` to provide protocol and port information alongside host details.
Only SRV records include port protocol bindings natively within DNS infrastructure.

Key Concept

DNS Record Types and Service Discovery (SRV Records)
Estimated Time:1m 30s
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