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Question 241

What is the purpose of the spanning-tree portfast bpduguard default global configuration command?

1. Enabling PortFast globally on all switch access ports.
2. Globally enabling BPDU guard on all ports that have PortFast enabled, putting violating ports into an error-disabled state.
3. Disabling Spanning Tree Protocol entirely across all switch interfaces to optimize forwarding speed.
4. Restricting switch port access exclusively to authorized static MAC addresses.

Correct Answer: 2

Explanation:

The spanning-tree portfast bpduguard default command is a powerful global configuration setting in Cisco IOS that streamlines security deployments across an entire enterprise campus switch network. When enabled, this command automatically activates Bridge Protocol Data Unit guard behavior on every switch port where PortFast has been enabled. Because PortFast is intended exclusively for edge ports connecting end-user workstations, IP phones, or servers, these ports should never receive BPDUs from another switch. If a user inadvertently or maliciously plugs a rogue switch or unauthorized bridge into an edge port, that device will typically generate BPDUs to participate in topology calculations. BPDU guard immediately intercepts these inbound control frames, determines that a security policy violation has occurred, and shuts down the port by placing it into an error-disabled state. This automated response prevents accidental bridging loops, topology corruption, and potential denial-of-service conditions from impacting the core production switching infrastructure without requiring manual per-interface configuration overhead.

Question 242

Which protocol is used to dynamically map IPv4 addresses to physical MAC addresses on a local network?

1. Domain Name System
2. Dynamic Host Configuration Protocol
3. Address Resolution Protocol
4. Internet Control Message Protocol

Correct Answer: 3

Explanation:

The Address Resolution Protocol is a foundational networking protocol operating within the Internet Protocol suite specifically designed to bridge the gap between Layer 3 logical addressing and Layer 2 physical hardware addressing. When a host needs to transmit data packets to another device residing on the exact same local network segment, it knows the target device’s IPv4 address from application configurations or routing lookups. However, network interface cards cannot encapsulate packets into Ethernet frames without knowing the destination’s 48-bit physical MAC address. To resolve this, the sending host broadcasts an ARP request packet across the local broadcast domain asking which device owns the specific target IPv4 address. The matching destination host responds directly with an ARP reply containing its physical hardware address. The originating host then caches this mapping in its local ARP table, allowing subsequent Ethernet frame encapsulations and transmissions to occur smoothly without continually repeating broadcast resolution queries across the local physical media.

Question 243

What is the administrative distance of an EIGRP summary route by default in Cisco IOS?

1. 90
2. 5
3. 170
4. 110

Correct Answer: 2

Explanation:

Administrative distance represents the trustworthiness and preference level assigned to different routing information sources on Cisco routers, where lower numerical values indicate higher reliability and priority during route selection. While standard internal routes learned via the Enhanced Interior Gateway Routing Protocol carry a default administrative distance of 90, EIGRP summary routes generated during route summarization processes are assigned a distinct and highly preferred administrative distance of 5 by default. This specialized low value ensures that summary routes take precedence over other component sub-routes and specific routing entries within the router’s decision-making algorithm. By prioritizing summary routes, routers can efficiently reduce overall routing table size, minimize memory utilization, and streamline path calculation overhead across large enterprise networks without risking routing loops or fragmented path selection conflicts between summarized advertisements and more granular internal network entries.

Question 244

Which command displays the current utilization of NVRAM and flash memory on a Cisco switch?

1. show running-config
2. show flash
3. show version
4. show ip interface brief

Correct Answer: 3

Explanation:

The show version command executed within privileged EXEC mode on Cisco routers and switches is an invaluable diagnostic utility that provides comprehensive system telemetry regarding hardware architecture, software versions, and persistent memory utilization. In addition to displaying exact Cisco IOS software image filenames, system uptime statistics, and hardware model numbers, the output explicitly details the total capacity, allocated usage, and remaining free space for both flash memory and non-volatile random-access memory. Flash memory stores large software packages, boot images, and auxiliary files, whereas NVRAM houses the persistent startup configuration file. System administrators frequently rely on the show version command during routine maintenance audits and pre-upgrade assessments to verify whether sufficient storage space exists in flash memory before transferring new Cisco IOS firmware images via TFTP or SCP servers, preventing failed update procedures and corrupted boot sequences.

Question 245

What is the primary operational function of a Layer 3 switch compared to a traditional Layer 2 switch?

1. Encrypting all wireless data payloads against unauthorized eavesdropping across local links.
2. Providing high-speed hardware-based Layer 2 switching combined with inter-VLAN Layer 3 routing capabilities.
3. Automatically assigning dynamic IP address lease configurations to client workstations on demand.
4. Translating private internal IP addresses into public routable addresses using port overload.

Correct Answer: 2

Explanation:

A Layer 3 switch represents an advanced networking device that integrates traditional high-speed Layer 2 Ethernet frame switching with high-performance Layer 3 packet routing capabilities within a single physical hardware platform. Traditional Layer 2 switches operate exclusively by examining MAC addresses and forwarding frames within the same VLAN or bridging separate segments, requiring an external router to route traffic between different VLANs. In contrast, a multilayer switch utilizes specialized Application-Specific Integrated Circuits to perform hardware-based routing decisions at wire speed across multiple virtual local area networks. By eliminating the traditional router-on-a-stick bottleneck and reducing latency associated with external router links, Layer 3 switches provide exceptional routing throughput, dense port scalability, and robust inter-VLAN performance, making them the standard architectural choice for enterprise distribution and core network layers.

Question 246

Which IPv6 address type is routable only within a single local link and never forwarded by routers?

1. Global Unicast Address
2. Unique Local Address
3. Link-Local Address
4. Anycast Address

Correct Answer: 3

Explanation:

An IPv6 Link-Local Address is a specialized unicast address type that is automatically configured on every IPv6-enabled network interface as soon as the protocol stack initializes, utilizing the reserved prefix fe80::/10. Link-local addresses are strictly restricted to the local physical or logical link where the host resides. A fundamental rule of IPv6 architecture dictates that routers must never forward packets containing link-local source or destination addresses outside the local network segment, effectively bounding their operational scope. Despite this non-routable restriction, link-local addresses are vital for core network operations. They serve as the mandatory source addresses for Neighbor Discovery Protocol messages, Router Solicitations, Router Advertisements, and dynamic routing protocol peering sessions between adjacent routers on the same shared medium. This ensures robust local neighbor communication before global unicast or unique local addressing schemes are provisioned on client endpoints.

Question 247

What is the block size of an IPv4 subnet with the mask 255.255.255.192?

1. 32 addresses
2. 64 addresses
3. 128 addresses
4. 256 addresses

Correct Answer: 2

Explanation:

To determine the block size or total address count of an IPv4 subnet, network engineers subtract the decimal value of the final octet of the subnet mask from the absolute base of 256. For a subnet mask of 255.255.255.192, the decimal value in the final octet is 192. Subtracting 192 from 256 yields a precise block size of 64 total addresses per subnet. This configuration corresponds to a /26 CIDR prefix in binary notation, where the final octet begins with two network bits set to one, leaving six bits for host device assignment. Out of the 64 total addresses in this block, two addresses are permanently reserved—the network identifier at the lowest boundary and the direct broadcast address at the highest boundary. This leaves exactly 62 usable host IP addresses available for assignment to workstations, servers, or router interfaces within that specific subnet range, offering an efficient intermediate subnetting boundary for enterprise network designs.

Question 248

Which TCP flag is used to reset a connection abruptly when an error or rejection occurs?

1. SYN
2. ACK
3. FIN
4. RST

Correct Answer: 4

Explanation:

The Reset flag is an essential control flag utilized within the Transmission Control Protocol header to handle exceptional error conditions, invalid segments, or abrupt connection terminations. Unlike the graceful teardown process managed by the FIN flag—which allows both communicating hosts to flush buffers and acknowledge remaining data streams—the RST flag forces an immediate and unceremonious teardown of the TCP session. When a host receives a packet destined for a closed port or encounters a severe protocol violation, it transmits a segment with the RST flag set. Upon receiving this reset segment, the remote host immediately drops the connection, clears allocated socket memory, and aborts any pending transmission queues without waiting for acknowledgments. This mechanism protects system resources against half-open connections, unauthorized scanning attempts, and persistent communication lockups when applications crash or reject incoming traffic unexpectedly.

Question 249

Which command enables password encryption globally on a Cisco IOS device?

1. enable secret password
2. service password-encryption
3. line console 0 password
4. crypto key generate rsa

Correct Answer: 2

Explanation:

The service password-encryption command is a critical global configuration command in Cisco IOS designed to enhance device security by obfuscating plain-text passwords stored within running and startup configuration files. By default, passwords configured for console lines, auxiliary lines, and virtual terminal (vty) remote login sessions are stored in clear text within configuration files, making them easily readable to anyone with viewing access to the running configuration or backup files. When an administrator executes service password-encryption, Cisco IOS applies a reversible cryptographic algorithm to scramble these plain-text strings into type-7 encrypted hashes. While type-7 encryption is relatively weak and easily reversible by dedicated decryption utilities, it successfully prevents casual observers from reading administrator passwords on screen or in configuration text backups. For maximum security on privileged execution access, administrators should always supplement this by utilizing the enable secret command, which applies a robust, non-reversible cryptographic hash.

Question 250

Which IEEE standard defines Rapid Spanning Tree Protocol (RSTP)?

1. IEEE 802.3
2. IEEE 802.1Q
3. IEEE 802.1w
4. IEEE 802.11

Correct Answer: 3

Explanation:

The IEEE 802.1w standard specifies the Rapid Spanning Tree Protocol, which was developed as a high-speed evolutionary replacement for the original, legacy IEEE 802.1D Spanning Tree Protocol. Traditional STP convergence times often ranged from thirty to fifty seconds as ports transitioned sluggishly through blocking, listening, and learning states, leading to noticeable network downtime during topology changes. RSTP dramatically improves upon this architecture by introducing new port roles and state simplifications, allowing link failures and topology reconvergencies to occur in milliseconds rather than minutes. By utilizing explicit handshake mechanisms between neighboring switches on point-to-point links, RSTP eliminates legacy forwarding delays, ensures rapid loop prevention, and maintains high availability across modern switched enterprise networks.

Question 251

What is the primary function of an Access Control List (ACL) configured on a Cisco router?

1. Dynamically leasing IP addresses to client workstations on demand.
2. Filtering network traffic by permitting or denying packets based on predefined criteria.
3. Translating private internal IP addresses into public routable addresses.
4. Resolving human-readable domain names into numerical IP addresses.

Correct Answer: 2

Explanation:

An Access Control List is a sequential collection of permit and deny statements applied to router interfaces to filter network traffic passing through the device. ACLs examine packet headers against criteria such as source and destination IP addresses, protocol types, and TCP or UDP port numbers. Routers evaluate packets against ACL statements sequentially from top to bottom; if a match occurs, the specified action is executed immediately, and remaining rules are bypassed. If no match is found, an implicit “deny all” rule drops the packet. Network administrators utilize ACLs extensively to enforce security policies, restrict unauthorized access to sensitive network segments, control routing update exchanges, and prioritize specific application traffic across enterprise network infrastructures.

Question 252

Which command displays the operational status of trunk ports and active VLAN tagging details on a Cisco switch?

1. show ip interface brief
2. show interfaces trunk
3. show cdp neighbors detail
4. show ip route

Correct Answer: 2

Explanation:

The show interfaces trunk command is an essential diagnostic and verification utility executed in privileged EXEC mode within the Cisco IOS command-line interface. When invoked, it displays all physical and logical switch ports currently operating as 802.1Q trunk links. The output details critical configuration parameters including the encapsulation type in use, native VLAN assignments, operational trunk status, allowed VLANs on the trunk, and VLANs currently active in the spanning tree forwarding state. Network administrators rely heavily on this command during campus network troubleshooting to verify whether inter-switch trunking is functioning correctly, confirm VLAN propagation across switches, and rapidly diagnose misconfigurations causing connectivity failures between separated virtual local area networks.

Question 253

What type of IPv6 address is ff02::1?

1. Global Unicast Address
2. Unique Local Address
3. All-Nodes Multicast Address
4. Link-Local Address

Correct Answer: 3

Explanation:

The address ff02::1 is a well-known IPv6 All-Nodes Multicast Address. Within IPv6 architecture, multicast addresses are utilized to deliver packets to multiple destination interfaces simultaneously within a defined scope. The prefix ff02:: designates link-local scope, meaning packets sent to this address will never be routed beyond the local physical link or broadcast domain. Specifically, ff02::1 targets every IPv6-enabled node or device residing on that local network segment. Operating systems and routers utilize this multicast address extensively for Neighbor Discovery Protocol communications, router solicitations, and local diagnostic pings without needing to broadcast frames across every host individually, thereby optimizing local bandwidth utilization and network efficiency.

Question 254

Which OSI layer handles data compression, encryption, and structural formatting of application data?

1. Physical Layer
2. Transport Layer
3. Presentation Layer
4. Network Layer

Correct Answer: 3

Explanation:

The Presentation layer, which is Layer 6 of the OSI reference model, is responsible for managing how data is presented to the application layer in a syntax that both communicating systems can understand and process. Functions operating at this layer include data compression to reduce bandwidth consumption, cryptographic encryption and decryption for secure sessions, and character set translations between different computer architectures—such as converting between ASCII and EBCDIC data representations. By standardizing data formatting formats and encryption wrappers, the presentation layer ensures that application payloads transmitted across disparate operating systems and hardware platforms remain fully legible, secure, and properly interpreted by receiving software applications without requiring application developers to code custom translation routines.

Question 255

What is the default administrative distance assigned to Routing Information Protocol (RIP) routes in Cisco IOS?

1. 1
2. 90
3. 110
4. 120

Correct Answer: 4

Explanation:

Administrative distance represents the trustworthiness or preference level of a routing information source on Cisco routers, where lower numerical values indicate higher reliability during route selection. In Cisco IOS routing architecture, the Routing Information Protocol is assigned a default administrative distance of 120. This relatively high value positions RIP as less trustworthy than OSPF at 110, EIGRP at 90, static routes at 1, and directly connected routes at 0. When a router learns about the exact same destination network from multiple routing protocols simultaneously, its path selection algorithm evaluates the administrative distances first, preferring sources with lower values. Consequently, a router will always prefer an OSPF or EIGRP route over a RIP route, making RIP suitable primarily for simple legacy environments rather than complex multi-protocol enterprise core networks.

Question 256

Which TCP port is utilized by default for unencrypted Hypertext Transfer Protocol web traffic?

1. Port 21
2. Port 23
3. Port 80
4. Port 443

Correct Answer: 3

Explanation:

Hypertext Transfer Protocol operates by default over TCP port 80. HTTP is the foundational application layer protocol used on the World Wide Web for fetching resources, transmitting web pages, and enabling communication between web browsers and web servers. Because standard HTTP transmits all data, form inputs, session tokens, and web content in plain text across the network, it is vulnerable to eavesdropping and interception by malicious actors. To secure web communications against unauthorized access and man-in-the-middle attacks, modern web infrastructure utilizes HTTPS, which wraps HTTP traffic inside Transport Layer Security or Secure Sockets Layer encryption and operates by default over TCP port 443. Network administrators frequently reference these standard port numbers when configuring firewalls, access control lists, and network address translation rules for web servers.

Question 257

What is the functional equivalent of the Cisco IOS copy running-config startup-config command?

1. reload
2. write memory
3. erase startup-config
4. show running-config

Correct Answer: 2

Explanation:

The write memory command (often abbreviated as wr or wr mem) is a legacy Cisco IOS command that performs the exact same operational function as copy running-config startup-config. Both commands take the active configuration file currently residing in volatile random-access memory and save it permanently into non-volatile random-access memory (NVRAM). When a network device undergoes a power cycle or system reboot, volatile RAM contents are wiped clean, while NVRAM contents persist. Therefore, executing write memory ensures that recent interface changes, routing policies, and security configurations are successfully preserved and loaded into memory upon the next system boot. While copy running-config startup-config is the modern standard syntax taught in Cisco certifications, write memory remains fully supported across virtually all Cisco IOS platforms for backward compatibility.

Question 258

Which wireless security protocol introduced the Temporal Key Integrity Protocol (TKIP) as an interim fix for vulnerable WEP encryption?

1. WPA
2. WPA2
3. WPA3
4. WPS

Correct Answer: 1

Explanation:

Wi-Fi Protected Access was introduced by the Wi-Fi Alliance as an interim security enhancement designed to replace the highly vulnerable Wired Equivalent Privacy protocol without requiring users to purchase brand-new hardware. WPA incorporated the Temporal Key Integrity Protocol to address WEP’s critical cryptographic flaws, specifically by implementing a per-packet key mixing system, message integrity check mechanisms, and larger initialization vectors to prevent key reuse attacks. While WPA provided vastly superior protection compared to WEP, TKIP still relied on underlying RC4 cryptographic principles that eventually became vulnerable to sophisticated exploits. Consequently, WPA was superseded by WPA2, which mandated robust Advanced Encryption Standard (AES) encryption combined with CCMP to establish secure enterprise-grade wireless local area networks.

Question 259

What is the total number of IP addresses available in an IPv4 subnet utilizing a /24 CIDR prefix?

1. 64 addresses
2. 128 addresses
3. 256 addresses
4. 512 addresses

Correct Answer: 3

Explanation:

A /24 CIDR prefix indicates an IPv4 subnet mask of 255.255.255.0, where twenty-four bits are allocated to network identification and eight bits are available for host device addressing. To calculate the total number of IP addresses in any subnet, determine the number of host bits and calculate two raised to that power. For a /24 prefix, raising two to the power of eight yields 256 total addresses in the block. Out of these 256 total addresses, exactly two are permanently reserved for structural functions: the lowest address represents the network identifier, and the highest address serves as the directed broadcast address. This leaves 254 usable host IP addresses available for assignment to workstations, servers, and router interfaces within that specific subnet range.

Question 260

Which Cisco IOS command displays the Layer 2 MAC address forwarding table on a switch?

1. show ip route
2. show mac address-table
3. show ip interface brief
4. show interfaces trunk

Correct Answer: 2

Explanation:

The show mac address-table command (also known as show mac-address-table depending on the Cisco IOS version) is a vital diagnostic command executed in privileged EXEC mode on Cisco switches. It displays the switch’s dynamic and static Layer 2 forwarding table, detailing which hardware MAC addresses have been learned on specific physical or logical switch ports, along with their associated VLAN assignments. Switches build this table dynamically by examining the source MAC addresses of incoming Ethernet frames. Network engineers rely on this command during troubleshooting to verify device connectivity, locate where a specific workstation or server is physically plugged into the campus network infrastructure, and diagnose MAC flooding or spanning tree routing issues.