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Question 221

Which IEEE standard defines VLAN tagging on Ethernet frames across trunk links?

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

Correct Answer: 2

Explanation:

The IEEE 802.1Q standard specifies the protocol for Virtual Bridged Local Area Networks, commonly known as VLAN tagging. When frames traverse a trunk link connecting switches, an 802.1Q tag—consisting of a Tag Protocol Identifier and Tag Control Information containing the VLAN ID—is inserted into the Ethernet frame header. This allows switches to differentiate traffic belonging to separate logical networks sharing the same physical trunk wire.

Question 222

Which sublayer of the Data Link layer is responsible for logical link control, flow control, and error handling independently of physical media?

1. Media Access Control sublayer
2. Logical Link Control sublayer
3. Physical Coding sublayer
4. Framing Control sublayer

Correct Answer: 2

Explanation:

The Data Link layer of the OSI model is divided into two primary sublayers: the Logical Link Control sublayer and the Media Access Control sublayer. The LLC sublayer (IEEE 802.2) acts as an interface between the upper network layer protocols and the lower media-specific hardware. It handles software-based framing, flow control, and error acknowledgment functions, allowing network layer protocols like IPv4 to operate seamlessly across diverse physical media types.

Question 223

What range of IPv4 addresses is designated for multicast communication (Class D)?

1. 1.0.0.0 to 126.255.255.255
2. 128.0.0.0 to 191.255.255.255
3. 224.0.0.0 to 239.255.255.255
4. 240.0.0.0 to 255.255.255.255

Correct Answer: 3

Explanation:

In traditional classful IPv4 addressing, Class D addresses spanning from 224.0.0.0 to 239.255.255.255 are specifically reserved for multicast transmissions. Unlike unicast communication intended for a single destination host or broadcast traffic targeting all nodes on a subnet, multicast addresses enable efficient one-to-many data distribution to specific groups of subscribed hosts across local and routed internetworks.

Question 224

What is the primary function of ROMMON mode in a Cisco router or switch?

1. Executing active routing protocol updates at wire speed.
2. Providing low-level boot diagnostics, password recovery, and software image recovery.
3. Storing permanent startup configuration files across reboots.
4. Managing virtual terminal remote login sessions.

Correct Answer: 2

Explanation:

ROM Monitor is a low-level operating mode utilized during device initialization or system troubleshooting on Cisco hardware. ROMMON mode runs directly from Read-Only Memory when the device cannot locate a valid Cisco IOS software image in flash memory, or when an administrator manually interrupts the boot sequence. It provides essential diagnostic utilities, password recovery procedures, and bootstrap commands to load new operating system images via TFTP or console connections.

Question 225

How does an OSPF-enabled router select its Router ID if no explicit loopback interface is configured?

1. The highest MAC address among all active interfaces.
2. The highest active IPv4 address among all active physical interfaces.
3. The lowest IP address configured on any interface.
4. A random 32-bit number generated at boot time.

Correct Answer: 2

Explanation:

The OSPF Router ID is a 32-bit identifier used to uniquely identify a router within an OSPF domain. When determining the Router ID, OSPF evaluates configured loopback interfaces first, selecting the highest IP address among them. If no loopback interfaces exist, the router selects the highest active IPv4 address configured among all its operational physical interfaces at the moment the OSPF process initializes.

Question 226

What is the correct sequence of Spanning Tree Protocol port states from initial link connection to operational data forwarding?

1. Blocking, Listening, Learning, Forwarding
2. Listening, Blocking, Forwarding, Learning
3. Learning, Blocking, Listening, Forwarding
4. Forwarding, Learning, Listening, Blocking

Correct Answer: 1

Explanation:

In standard 802.1D Spanning Tree Protocol, when a switch port becomes active, it transitions through a deliberate sequence of states to prevent temporary bridging loops: Blocking, Listening, Learning, and finally Forwarding. During Listening and Learning states, the switch processes BPDUs and populates its MAC address table without forwarding user data traffic, taking approximately thirty to fifty seconds to reach the operational Forwarding state.

Question 227

Which wireless encryption protocol introduced robust AES-CCMP encryption to replace vulnerable WEP security mechanisms?

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

Correct Answer: 3

Explanation:

Wi-Fi Protected Access 2 was introduced to provide enterprise-grade wireless security by implementing the Advanced Encryption Standard encryption algorithm combined with Cipher Block Chaining Message Authentication Code Protocol. WPA2 completely replaced the insecure Wired Equivalent Privacy protocol and the interim WPA-TKIP standard, establishing strong cryptographic integrity and confidentiality for wireless local area networks.

Question 228

What mechanism allows an IPv6 host to configure its own global unicast address automatically without requiring a DHCPv6 server?

1. Address Resolution Protocol
2. Stateless Address Autoconfiguration
3. Dynamic Host Configuration Protocol
4. Network Time Protocol

Correct Answer: 2

Explanation:

Stateless Address Autoconfiguration is a core feature of IPv6 that enables a host to generate its own unique global unicast address independently. By combining a 64-bit network prefix advertised by local routers via Router Advertisement messages with a 64-bit interface identifier generated via EUI-64 or randomized privacy extensions, the host configures valid IP settings without needing stateful DHCPv6 tracking servers.

Question 229

What is a primary operational characteristic of the User Datagram Protocol compared to Transmission Control Protocol?

1. Connection-oriented session establishment with explicit three-way handshakes.
2. Guaranteed, reliable, ordered delivery of all transmitted data packets.
3. Lightweight, connectionless data datagram transmission without error recovery or flow control.
4. Sliding window flow control to prevent receiver buffer overflow.

Correct Answer: 3

Explanation:

The User Datagram Protocol is a lightweight, connectionless transport layer protocol operating at Layer 4 of the OSI model. Unlike TCP, UDP does not establish pre-delivery connections, perform handshakes, track sequence numbers, or provide retransmission mechanisms for lost packets. This minimalist design minimizes overhead and latency, making UDP ideal for real-time applications such as Voice over IP, video streaming, and DNS queries where speed takes precedence over absolute reliability.

Question 230

Which TCP port is utilized by default for Secure Shell remote management connections?

1. Port 21
2. Port 23
3. Port 22
4. Port 80

Correct Answer: 3

Explanation:

Secure Shell operates by default over TCP port 22. SSH provides cryptographic encapsulation for remote terminal management, secure file transfers, and port forwarding, serving as the secure industry standard replacement for unencrypted legacy protocols such as Telnet operating on port 23 and FTP operating on port 21.

Question 231

How many usable host IP addresses are available in an IPv4 subnet utilizing a /29 CIDR prefix?

1. 2 hosts
2. 6 hosts
3. 14 hosts
4. 30 hosts

Correct Answer: 2

Explanation:

A /29 CIDR prefix corresponds to a subnet mask of 255.255.255.248, leaving 3 bits for host device assignment. Calculating total addresses using two to the power of 3 yields 8 total addresses. Subtracting 2 addresses for the network identifier and the broadcast address leaves 6 usable host IP addresses available for device configuration.

Question 232

Which command transitions a Cisco IOS CLI session from User EXEC mode to Privileged EXEC mode?

1. configure terminal
2. enable
3. router ospf 1
4. write memory

Correct Answer: 2

Explanation:

The enable command executed at the User EXEC prompt (indicated by the > symbol) prompts the administrator for an enable password and transitions the session to Privileged EXEC mode (indicated by the # symbol). Privileged EXEC mode grants access to diagnostic commands, configuration backup tools, and global configuration mode entry.

Question 233

What is the default port security violation mode on Cisco switches when a security breach occurs?

1. Protect
2. Restrict
3. Shutdown
4. Warning

Correct Answer: 3

Explanation:

Port security allows administrators to restrict switch port access based on registered source MAC addresses. If a violation occurs—such as an unauthorized device connecting to a secured port—the default violation mode is shutdown. In this mode, the switch immediately disables the interface, puts it into an error-disabled state, and generates a syslog alert until an administrator manually resets the port.

Question 234

What is the default administrative distance assigned to OSPF routes in Cisco IOS?

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

Correct Answer: 3

Explanation:

Administrative distance represents the trustworthiness of a routing protocol source, where lower values indicate higher preference. In Cisco IOS, OSPF is assigned a default administrative distance of 110. This positions OSPF as more trustworthy than RIP at 120, but less preferred than EIGRP at 90, static routes at 1, and directly connected routes at 0.

Question 235

What network address translation technology allows multiple internal private hosts to share a single public IP address using unique source port numbers?

1. Static NAT
2. Dynamic NAT
3. Port Address Translation
4. IPv6 Tunneling

Correct Answer: 3

Explanation:

Port Address Translation, also known as NAT Overload, is a form of Network Address Translation that maps multiple private internal IP addresses to a single public IP address by tracking unique TCP or UDP transport layer source port numbers. This efficient mechanism conserves scarce public IPv4 address blocks while enabling entire enterprise networks to access the internet simultaneously.

Question 236

What is the first message transmitted by a client workstation initiating a DHCP lease negotiation?

1. DHCP OFFER
2. DHCP REQUEST
3. DHCP DISCOVER
4. DHCP ACKNOWLEDGE

Correct Answer: 3

Explanation:

Dynamic Host Configuration Protocol communication follows the DORA process: Discover, Offer, Request, Acknowledge. The process begins when a newly connected client workstation broadcasts a DHCP DISCOVER message across the local network segment to locate any available DHCP servers capable of providing IP configuration parameters.

Question 237

What is the primary operational purpose of configuring BPDU guard on PortFast-enabled switch access ports?

1. Encrypting spanning tree control frames across trunk links.
2. Preventing unauthorized switches from connecting to access ports and disrupting the spanning tree topology.
3. Automatically increasing trunk link bandwidth during heavy congestion.
4. Translating rapid spanning tree protocol metrics into legacy STP values.

Correct Answer: 2

Explanation:

BPDU guard is a security feature configured on PortFast access ports where end devices connect. If a rogue switch is plugged into a PortFast port and begins transmitting Bridge Protocol Data Units, BPDU guard immediately detects the incoming BPDUs and puts the port into an error-disabled state. This protects the switched network topology from unexpected loops and unauthorized bridge insertions.

Question 238

What is the primary function of the Frame Check Sequence trailer within an Ethernet frame?

1. Identifying the source MAC address of the transmitting node.
2. Verifying frame integrity by detecting transmission errors via Cyclic Redundancy Check algorithms.
3. Encrypting payload data against unauthorized wireless interception.
4. Indicating the upper-layer network protocol encapsulated in the payload.

Correct Answer: 2

Explanation:

The Frame Check Sequence is a 4-byte trailer appended to the end of an Ethernet frame. It contains a Cyclic Redundancy Check mathematical value calculated by the sending device based on frame contents. When the receiving device processes the frame, it recalculates the CRC. If the calculated value matches the FCS trailer, the frame is accepted as error-free; otherwise, the corrupted frame is dropped immediately.

Question 239

Where should an Extended Access Control List ideally be placed within a network topology?

1. As close to the destination network as possible.
2. As close to the source of the traffic as possible.
3. Only on loopback management interfaces.
4. Exclusively on core distribution routers.

Correct Answer: 2

Explanation:

Best practices in network security dictate that Extended Access Control Lists should be placed as close as possible to the source of the unauthorized or filtered traffic. By blocking unwanted packets near the source interface, routers prevent wasteful bandwidth utilization across enterprise core links and wide area networks, dropping malicious or unauthorized traffic before it traverses the network infrastructure.

Question 240

What Syslog severity level corresponds to an emergency condition where the system is completely unusable?

1. Level 0
2. Level 3
3. Level 4
4. Level 7

Correct Answer: 1

Explanation:

Syslog severity levels range from 0 to 7, where lower numerical values represent higher urgency and severity. Level 0 corresponds to Emergency conditions where the system is unusable. The complete scale progresses from Level 0 Emergency, Level 1 Alert, Level 2 Critical, Level 3 Error, Level 4 Warning, Level 5 Notice, Level 6 Informational, up to Level 7 Debugging.