Question 1

Inter-switch VLAN communication: Which technologies allow VLAN traffic tagging across switches? Options: ISL, VTP, 802.1Q, 802.3z

Accepted Answer

Introduction / Context: Switch-to-switch VLAN communication requires trunking protocols that encapsulate VLAN membership inside Ethernet frames. Cisco and IEEE standards differ. Given Data / Assumptions: Protocols listed: ISL (Cisco), VTP, 802.1Q, 802.3z Concept / Approach: ISL and 802.1Q are VLAN trunking protocols. VTP is for VLAN database management, not tagging. 802.3z refers to Gigabit Ethernet physical standard, not VLAN tagging. Step-by-Step Solution: ISL: Encapsulates VLAN IDs.802.1Q: IEEE standard VLAN tagging.VTP: Only distributes VLAN info, no frame tagging.802.3z: Physical Gigabit spec, not VLAN-specific. Verification / Alternative check: Refer to Cisco docs: ISL and 802.1Q explicitly define VLAN tagging. Why Other Options Are Wrong: VTP: Manages VLAN info, no frame encapsulation. 802.3z: Gigabit Ethernet, not trunking. Common Pitfalls: Confusing VTP’s VLAN management with inter-switch tagging; mixing physical layer with encapsulation protocols. Final Answer: 1 and 3 (ISL and 802.1Q)

Question 2

IEEE VLAN tagging configuration: Which command sets a switch port to use the IEEE 802.1Q trunk encapsulation standard?

Accepted Answer

Introduction / Context: IEEE 802.1Q is the standard method of VLAN tagging. Cisco switches must be configured to use ISL (Cisco proprietary) or 802.1Q. Given Data / Assumptions: We want to use IEEE standard VLAN tagging. Correct IOS syntax is required. Concept / Approach: Interface configuration mode is needed. The keyword “dot1q” corresponds to 802.1Q tagging. Step-by-Step Solution: Enter interface config mode.Command: switchport trunk encapsulation dot1q.Applies 802.1Q tagging to that trunk port. Verification / Alternative check: Run show interface trunk to confirm encapsulation. Why Other Options Are Wrong: ISL: Cisco proprietary, not IEEE. IETF: Not valid syntax in IOS. Global config mode syntax is wrong; must be under interface. Common Pitfalls: Entering command in global mode instead of interface mode. Final Answer: Switch(config-if)# switchport trunk encapsulation dot1q

Question 3

Troubleshooting VLAN access: A new host is connected to a switch but cannot log into the server on the same switch. What is the most likely issue?

Accepted Answer

Introduction / Context: Hosts connected to the same switch must belong to the same VLAN to communicate without routing. Misconfigured VLAN assignment is a common cause of access issues. Given Data / Assumptions: New host connected to switch port. Cannot communicate with server on same switch. Concept / Approach: Switches segment traffic into VLANs. If the host port and server port are not in the same VLAN, frames will not be forwarded between them without an L3 device. Step-by-Step Solution: Check VLAN membership on both ports.If mismatched VLAN IDs, host and server cannot see each other.Correct by configuring both ports into the same VLAN. Verification / Alternative check: Run show vlan brief to confirm port VLAN assignment. Why Other Options Are Wrong: A: Router not required if both devices are in same VLAN. B: VTP propagates VLAN info but not per-host config. C: Invalid MAC would prevent switch registration, rare scenario. E: Server NIC issue would affect all connections, not just this host. Common Pitfalls: Assuming VTP handles host-specific access; overlooking VLAN port assignment checks. Final Answer: The switch port is not configured to the correct VLAN membership.

Question 4

VLAN fundamentals: Which of the following statements about VLANs is true?

Accepted Answer

Introduction / Context: Virtual LANs (VLANs) segment networks logically. Cisco uses the VLAN Trunking Protocol (VTP) to manage and propagate VLAN information across switches. Given Data / Assumptions: We want the correct fact about VLAN/VTP operation. Concept / Approach: VTP allows a central switch to manage VLAN additions/deletions and propagate them to others within the same VTP domain. Step-by-Step Solution: Check each statement.Correct: VTP distributes VLAN info within a domain.Other statements are misconceptions or inaccurate. Verification / Alternative check: Use show vtp status to confirm domain and VLAN counts. Why Other Options Are Wrong: A: Only one VLAN is needed, not mandatory to have two. B: No such “fastest switch” concept; VLANs must be configured or propagated via VTP. C: Arbitrary limit of 10 switches is incorrect. E: Routers (or L3 switches) are only needed for inter-VLAN routing. Common Pitfalls: Confusing VTP’s role; assuming multiple VLANs are always mandatory. Final Answer: VTP is used to send VLAN information to switches in a configured VTP domain.

Question 5

VTP default behavior: Which statement is true about VLAN Trunking Protocol (VTP) by default on Cisco switches?

Accepted Answer

Introduction / Context: VTP simplifies VLAN management across Cisco switches. Understanding default VTP mode is critical for configuration and troubleshooting. Given Data / Assumptions: Switch type: Cisco Catalyst Default VTP mode must be identified Concept / Approach: When powered on, Cisco switches default to VTP server mode. In this mode, VLAN changes can be created, modified, or deleted and propagated to other switches in the same VTP domain. Step-by-Step Solution: Confirm default: VTP server mode on new Cisco switch.This allows creation of VLANs locally until VTP mode is explicitly changed. Verification / Alternative check: Run show vtp status; newly initialized switch will show mode = server. Why Other Options Are Wrong: B: Transparent is optional, not default. C: Default domain name is null, not “Cisco.” D: Default is not client mode. E: VTP is active by default, not disabled. Common Pitfalls: Misremembering default domain name; confusing transparent with server mode. Final Answer: All switches are VTP servers by default.

Question 6

VLAN design benefits in enterprise switching: Which of the following are true benefits of using Virtual LANs (VLANs)? Consider the statements below and choose the correct combination: 1) They increase the size of collision domains. 2) They allow log…

Accepted Answer

Introduction / Context: Virtual LANs (VLANs) are a foundational Layer 2 technology in enterprise networks. They let administrators logically segment traffic on the same physical switch fabric, improving manageability, performance, and security. This question tests recognition of the real, widely accepted benefits of VLANs versus common misconceptions. Given Data / Assumptions: Statements 1–6 describe possible VLAN characteristics. We must pick the set that lists true benefits. Concept / Approach: VLANs create separate broadcast domains at Layer 2. By splitting one big broadcast domain into multiple smaller ones, VLANs reduce broadcast scope, allow logical user grouping, and help contain security risks. Collision domains are determined by switch ports and are not made larger by VLANs. Step-by-Step Solution: Check 2: VLANs enable logical grouping by function or department. This is a core reason to deploy VLANs. ✔Check 3: VLANs can enhance security by isolating traffic between groups and enforcing inter-VLAN policy at Layer 3. ✔Check 6: Creating more VLANs increases the number of broadcast domains while reducing the size of each one. ✔Check 1: Collision domains are per switch port; VLANs do not increase collision domain size. ✖Check 4: This reverses the usual effect; VLANs do not increase broadcast domain size. ✖Check 5: While VLANs often simplify administration, the option set required by the question expects exactly items 2, 3, and 6. Verification / Alternative check: Consider a switch with one VLAN versus three VLANs. With three VLANs, each VLAN’s broadcast traffic is contained, proving that the number of broadcast domains increases while each domain’s size decreases. Why Other Options Are Wrong: 1 and 5: 1 is false; VLANs do not increase collision domain size. 2 and 4: 4 is false; VLANs reduce, not enlarge, broadcast domain size. 1, 3 and 5: 1 is false, so the combination fails. 2, 3, 5 and 6: Contains correct items but adds 5, which the question’s intended correct set does not include. Common Pitfalls: Confusing collision domains (per port) with broadcast domains (per VLAN), and assuming VLANs always simplify operations without considering configuration design. Final Answer: 2, 3 and 6

Question 7

VTP (VLAN Trunking Protocol) prerequisites: To communicate VLAN information between two Cisco switches using VTP, which requirements must be met?

Accepted Answer

Introduction / Context: VLAN Trunking Protocol (VTP) allows Cisco switches to share VLAN configuration within a VTP domain. Knowing the minimal requirements for VTP to work is essential for quick deployments and troubleshooting. Given Data / Assumptions: Candidate requirements include same VTP domain name, VTP server presence, encapsulation types, access-port settings, cabling, and router involvement. Concept / Approach: For two switches to exchange VLAN information via VTP, they must share the same VTP management domain name and at least one device in that domain must be a VTP server to originate and propagate VLAN database updates. Step-by-Step Solution: Requirement 2: “The VTP management domain name of both switches must be set the same.” This is mandatory. ✔Requirement 4: “One of the two switches must be configured as a VTP server.” At least one server is required to advertise VLAN changes. ✔Requirement 1: “Each end of the trunk link must be set to the IEEE 802.1e encapsulation.” Invalid; Cisco uses 802.1Q (dot1q) or ISL (legacy), not “802.1e.” ✖Requirement 3: “All ports … must be set as access ports.” Incorrect; trunk ports are needed for VTP advertisements to pass. ✖Requirement 5: “A rollover cable is required …” Not required; standard switch-to-switch cabling (typically straight-through on modern devices) is used. ✖Requirement 6: “A router must be used to forward VTP traffic …” VTP is Layer 2 and does not require a router within the same domain. ✖ Verification / Alternative check: Use show vtp status on both switches to confirm the same VTP domain and verify at least one device is in server mode. Why Other Options Are Wrong: 1, 2 and 4: Includes item 1, which is invalid. 3, 5 and 6: None of these are required for VTP operation. 1 and 6: Both are incorrect requirements. 1, 2 and 6: Contains invalid items 1 and 6. Common Pitfalls: Forgetting to set a common VTP domain and neglecting to ensure at least one VTP server; confusing 802.1Q trunking with nonexistent “802.1e.” Final Answer: 2 and 4

Question 8

Configuring a trunk on a Cisco Catalyst 2960: Which command correctly configures a switchport as an IEEE 802.1Q trunk on a 2960 switch?

Accepted Answer

Introduction / Context: On Cisco Catalyst 2960 switches, enabling a trunk port is a frequent task to carry multiple VLANs between switches or between a switch and a router-on-a-stick. Understanding the exact command syntax prevents misconfiguration. Given Data / Assumptions: Platform: Catalyst 2960. Goal: Configure a port to operate as a VLAN trunk using 802.1Q. Concept / Approach: The 2960 supports only 802.1Q encapsulation and does not allow changing trunk encapsulation type. The correct approach is to enter interface configuration mode and set the switchport to trunk mode. Step-by-Step Solution: Enter interface configuration: interface fastethernet 0/x (or gigabitethernet as applicable).Apply command: switchport mode trunk.Optionally prune or allow VLANs: switchport trunk allowed vlan add/remove list. Verification / Alternative check: Use show interfaces trunk to verify the interface is in trunking mode and carrying expected VLANs. Why Other Options Are Wrong: trunk on / trunk all: Not valid IOS commands. switchport trunk on: Not valid syntax; the correct form uses “mode.” switchport encapsulation dot1q: On 2960, encapsulation is fixed to 802.1Q; this command is not available on that platform. Common Pitfalls: Trying to set encapsulation on platforms that do not support ISL; forgetting to allow specific VLANs if the default allowed list was modified elsewhere. Final Answer: switchport mode trunk

Question 9

IEEE frame tagging standard for VLAN trunking In Ethernet switching and inter-switch trunking, which of the following is the IEEE standard that defines frame tagging for Virtual LAN (VLAN) identification?

Accepted Answer

Introduction / Context: Modern switched networks commonly use VLANs to segment broadcast domains at Layer 2. When VLANs span multiple switches, trunk links must carry traffic for several VLANs simultaneously. To do this, Ethernet frames are tagged so that the receiving switch can identify the VLAN membership. This question asks you to identify the correct IEEE standard that specifies VLAN frame tagging. Given Data / Assumptions: The context is VLAN tagging on Ethernet trunks between switches or between a switch and a router (router-on-a-stick). We are comparing well-known standards and terms used in switching. The goal is to pick the official IEEE standard for tagging. Concept / Approach: The IEEE 802.1Q standard defines how an additional tag is inserted into the Ethernet frame header to identify the VLAN ID and priority information. This tag allows multiple VLANs to traverse the same physical link. Other options listed refer to different technologies or non-IEEE mechanisms and thus are not the correct answer for the standard that defines tagging itself. Step-by-Step Solution: Recognize that VLAN tagging across trunks is standardized by IEEE.Recall that IEEE 802.1Q inserts a 4-byte tag into Ethernet frames with fields including VLAN ID and priority.Note that Cisco ISL is proprietary and not an IEEE standard.Select 802.1Q as the correct IEEE tagging standard. Verification / Alternative check: Check any mainstream switch documentation: when configuring trunks, the encapsulation type is typically 802.1Q. Proprietary options like ISL are largely deprecated and were never standardized by IEEE. Why Other Options Are Wrong: ISL: Cisco-proprietary encapsulation, not an IEEE standard. 802.3Z: Refers to Gigabit Ethernet over fiber (1000BASE-X), not VLAN tagging. 802.3U: Refers to Fast Ethernet (100BASE-TX/FX), not VLAN tagging. 802.1D: Spanning Tree Protocol standard, unrelated to frame tagging. Common Pitfalls: Confusing ISL with 802.1Q because both tag frames; only 802.1Q is IEEE. Assuming any 802.3 substandard relates to VLANs; VLAN tagging is under 802.1 (bridging). Final Answer: 802.1Q

Question 10

Single connection router-on-a-stick for inter-VLAN routing A switch has three VLANs (VLAN 2, VLAN 3, and VLAN 4). To route between these VLANs using only one physical connection between the switch and the router, what type of Ethernet interface shou…

Accepted Answer

Introduction / Context: Inter-VLAN routing can be achieved with a single physical link between a router and a switch using the router-on-a-stick design. The router must support VLAN tagging (IEEE 802.1Q) on that interface, and subinterfaces are configured for each VLAN. The question focuses on which router interface type is appropriate when only one connection is used. Given Data / Assumptions: Three VLANs exist on the switch (2, 3, 4). Only one router-to-switch physical connection is allowed. 802.1Q trunking will carry multiple VLANs over a single Ethernet link. Concept / Approach: A router-on-a-stick requires one Ethernet interface that supports 802.1Q trunking and subinterfaces. Historically, Fast Ethernet (100 Mbps) has been the standard minimum interface speed in classic exam contexts, though Gigabit Ethernet also works. Serial interfaces (e.g., 56 Kbps) do not support Ethernet trunking, and multiple serials would not meet the single-link constraint. Step-by-Step Solution: Choose an Ethernet interface capable of trunking.Enable 802.1Q encapsulation on router subinterfaces.Assign each subinterface an IP in its VLAN’s subnet.Verify inter-VLAN routing via trunk link. Verification / Alternative check: Platform guides show that encapsulation dot1Q is configured on a router’s FastEthernet or GigabitEthernet subinterfaces to carry multiple VLANs on a single link. Why Other Options Are Wrong: 10Mbps Ethernet: Technically possible if it supports 802.1Q, but exams typically expect Fast Ethernet as the baseline. 56Kbps Serial: Not Ethernet; cannot carry 802.1Q frames. 1Gbps Ethernet: Also viable, but the canonical choice in traditional questions is Fast Ethernet. Multiport serial: Not relevant to VLAN trunking over Ethernet. Common Pitfalls: Confusing router-on-a-stick (single Ethernet, subinterfaces) with multilayer switching. Thinking that a separate physical link per VLAN is required; subinterfaces avoid that. Final Answer: 100Mbps Ethernet

Question 11

Improving performance and shrinking broadcast domains You need to both increase bandwidth available to hosts and reduce the size of Layer 2 broadcast domains across the network. Which option best accomplishes both objectives simultaneously?

Accepted Answer

Introduction / Context: As networks grow, two common goals are to increase per-user bandwidth and to reduce the impact of broadcast traffic. Layer 2 switches already help by creating separate collision domains per port, but broadcast frames still flood within the same VLAN. To shrink broadcast domains without adding routers at every segment, VLANs are used on switches to logically partition the network. Given Data / Assumptions: Requirement 1: Increase available bandwidth to endpoints. Requirement 2: Reduce the size of broadcast domains. Environment: Layer 2/Layer 3 Ethernet-based campus. Concept / Approach: Switches provide micro-segmentation, eliminating collisions and increasing effective bandwidth compared to hubs. However, all ports in a single VLAN still share a broadcast domain. Creating multiple VLANs on switches limits broadcast scope to the members of each VLAN. Inter-VLAN communication can be handled via a router or a multilayer switch, maintaining segmentation benefits while enabling controlled connectivity. Step-by-Step Solution: Replace or minimize hubs; deploy switches for per-port collision domains.Define VLANs based on organizational or functional boundaries.Assign switch ports to appropriate VLANs to limit broadcast flooding.Provide inter-VLAN routing where necessary (router-on-a-stick or multilayer switch). Verification / Alternative check: Measure broadcast traffic before and after VLAN deployment; observe reduced ARP and broadcast storms per VLAN. Throughput tests should show improved performance due to micro-segmentation and reduced unnecessary traffic. Why Other Options Are Wrong: Managed hubs: Still single collision domain; do not limit broadcast domains. Bridges: Reduce collision domains but scale poorly and still share broadcasts at segment level. Switches (no VLANs): Improve bandwidth but do not shrink broadcast domains. Repeaters: Purely physical-layer; no effect on bandwidth per user or broadcast domains. Common Pitfalls: Assuming switches alone reduce broadcast domains; VLANs are required for that. Forgetting inter-VLAN routing to enable necessary cross-VLAN communication. Final Answer: Switches configured with VLANs

Question 12

VTP modes and where VLAN changes are permitted In Cisco's VLAN Trunking Protocol (VTP), which switch mode specifically allows you to create, modify, and delete VLAN definitions that are then advertised to other switches in the same VTP domain?

Accepted Answer

Introduction / Context: VTP is a Cisco protocol that distributes VLAN configuration information across switches in the same VTP domain, reducing administrative overhead. Understanding what you can and cannot do in each mode (server, client, transparent) is essential for proper VLAN management and change control within a campus network. Given Data / Assumptions: VTP is enabled and switches share the same domain name. We need to know which mode permits making VLAN changes that will be propagated. Modes considered: server, client, transparent (STP is unrelated). Concept / Approach: In VTP server mode, you can add, delete, and rename VLANs; changes are advertised to other switches in the domain. In VTP client mode, the switch cannot create or delete VLANs; it only receives updates. In VTP transparent mode, the switch does not apply received updates to its VLAN database (it forwards them) but can manage VLANs locally (not distributed). Therefore, the mode that both allows changes and distributes them is server. Step-by-Step Solution: Identify the requirement: central VLAN changes with distribution.Map VTP modes to capabilities: server can create/propagate; client receives; transparent local-only.Select VTP server mode. Verification / Alternative check: Check the VTP status with show vtp status to confirm the mode and revision number. Only servers increment and propagate configuration revision numbers upon changes. Why Other Options Are Wrong: Client: Cannot create or delete VLANs. Transparent: Local changes only; no propagation to the domain database. STP: Not a VTP mode; it is a separate protocol (Spanning Tree). Off: Not relevant to VTP operations in this context. Common Pitfalls: Making changes in transparent mode expecting domain-wide propagation. Ignoring VTP revision numbers, which can overwrite domain VLANs if not managed carefully. Final Answer: Server

Question 13

Default VLANs permitted on a new 802.1Q trunk On an IOS-based switch, after creating a new 802.1Q trunk between switches, which VLANs are permitted across that trunk by default (before any pruning or allowed-vlan filtering is configured)?

Accepted Answer

Introduction / Context: When enabling an 802.1Q trunk on Cisco IOS switches, the default behavior determines which VLANs can traverse the link. Understanding the default allowed VLAN set helps avoid connectivity surprises and informs whether additional pruning or explicit switchport trunk allowed vlan commands are required. Given Data / Assumptions: Two Cisco IOS switches are connected via an 802.1Q trunk. No explicit allowed-vlan list or pruning has been configured yet. The question asks for the default behavior. Concept / Approach: By default, Cisco switches allow all VLANs across a newly formed trunk. Administrators can later restrict this with allowed-vlan lists or enable VTP pruning to limit unnecessary VLAN traffic. This default simplifies initial connectivity but may carry unneeded broadcasts if left unrestricted. Step-by-Step Solution: Create the trunk (for example, set mode to trunk or use DTP).Observe default allowed VLAN set: all VLANs.Optionally configure pruning or an explicit allowed list to match design. Verification / Alternative check: Use show interfaces trunk to see the allowed and active VLAN lists and confirm current behavior before and after changes. Why Other Options Are Wrong: Manual-only permission (B) is false; defaults allow all. Only configured VLANs (C) or only extended VLANs (D) are not the default behavior. Only VLAN 1 (E) is incorrect; although VLAN 1 is native by default, all VLANs are allowed unless restricted. Common Pitfalls: Leaving trunks unrestricted can spread broadcasts and security domains unnecessarily. Confusing the native VLAN concept (untagged) with the allowed VLAN list. Final Answer: By default, all VLANs are allowed on the trunk.

Question 14

Valid operational modes for a VLAN trunk port When configuring a Cisco switch port to operate as a VLAN trunk, which of the following port modes are valid in that trunking context (choose the correct grouping)?

Accepted Answer

Introduction / Context: Cisco switch ports can operate in different administrative modes related to trunk negotiation and access behavior. Understanding which modes actually pertain to trunking prevents configuration mistakes and helps you interpret show interfaces switchport outputs correctly. The options listed include both legitimate trunk negotiation modes and unrelated states from other protocols. Given Data / Assumptions: The modes presented are: Blocking, Dynamic auto, Dynamic desirable, Nonegotiate, Access, Learning. We must choose those that are valid modes used when a port is set up as, or negotiates, a trunk. Concept / Approach: Trunk-related administrative modes include dynamic auto (passively waits to form a trunk), dynamic desirable (actively tries to form a trunk), trunk (force trunk), and nonegotiate (do not run DTP; requires the far end to be hard-set). The options do not include the literal trunk keyword but do include the other relevant trunk-related modes. STP states such as blocking and learning are not port trunk modes, and access forces non-trunk operation. Step-by-Step Solution: Identify trunk negotiation modes: dynamic auto, dynamic desirable, nonegotiate.Discard non-trunk or non-administrative items: blocking, learning (STP states), access (non-trunk).Select the grouping that contains 2, 3, and 4. Verification / Alternative check: Command reference for switchport mode confirms valid options such as access, trunk, dynamic auto, dynamic desirable, and the switchport nonegotiate modifier for trunk links. Why Other Options Are Wrong: Blocking and Learning are STP states, not trunk modes. Access is specifically non-trunk. Other groupings include at least one invalid trunk-mode choice. Common Pitfalls: Confusing STP states with port mode settings. Using nonegotiate on one side without hard-setting trunk on the peer. Final Answer: 2, 3 and 4

Question 15

Automating VLAN distribution Which protocol minimizes administrative effort in a switched campus by distributing VLAN creation and name changes to all switches within the same management domain?

Accepted Answer

Introduction / Context: As the number of switches grows, manually creating and renaming VLANs on every device becomes time-consuming and error-prone. Cisco designed a mechanism to propagate VLAN database changes across switches that share a common domain to streamline operations and maintain consistency automatically. Given Data / Assumptions: The environment uses Cisco switches capable of VLAN management protocols. Goal: reduce manual VLAN configuration on each individual switch. Changes should propagate within a defined administrative boundary (domain). Concept / Approach: VTP (VLAN Trunking Protocol) distributes VLAN IDs and names across switches in a VTP domain. VTP server switches originate updates, client switches receive them, and transparent switches forward without applying them to their local VLAN database. This reduces repetitive tasks and helps maintain consistent VLAN provisioning. Step-by-Step Solution: Configure a shared VTP domain name and password (optional).Set core switches to server mode to originate updates.Set access switches to client mode to receive updates.Verify with: show vtp status. Verification / Alternative check: After adding a VLAN on a server, check that it appears on clients automatically and that the configuration revision number increments appropriately across the domain. Why Other Options Are Wrong: STP: Prevents loops; does not distribute VLAN info. DHCP: Allocates IP configuration; unrelated to VLAN databases. ISL: A frame-encapsulation method (Cisco-proprietary), not a distribution protocol. DTP: Negotiates trunking; does not propagate VLAN definitions. Common Pitfalls: Mismatched domain names or passwords prevent synchronization. Accidental introduction of a higher revision number can overwrite domain VLANs. Final Answer: VTP

Question 16

Protocols involved in configuring trunking on a switch Considering common Cisco switching terminology, which items below are actually used for VLAN trunking encapsulation or trunk configuration on a switch (select the correct combination from the li…

Accepted Answer

Introduction / Context: Trunking allows multiple VLANs to traverse a single physical link. Two well-known VLAN trunk encapsulations exist historically on Cisco gear: IEEE 802.1Q (open standard) and Cisco ISL (proprietary, largely deprecated). It is important to distinguish encapsulation protocols from management or distribution protocols like VTP. Given Data / Assumptions: The list includes: 1) VLAN Trunk Protocol, 3) VLAN 802.1Q, 4) ISL. We are asked which are used to configure trunking (that is, frame encapsulation on trunk ports). Concept / Approach: Trunk encapsulation is about how frames are tagged across a trunk. IEEE 802.1Q inserts a tag in the Ethernet frame; ISL encapsulates the entire frame in a Cisco header. VTP, despite its name (VLAN Trunk Protocol), is not an encapsulation; it distributes VLAN database information and does not determine the tagging method on trunks. Step-by-Step Solution: Identify encapsulation protocols: 802.1Q and ISL.Exclude VTP as it is for VLAN distribution, not encapsulation.Choose the option listing 3 and 4 together. Verification / Alternative check: On Cisco IOS, trunk encapsulation configuration uses switchport trunk encapsulation dot1q or isl (where supported). VTP is configured separately and does not appear in the encapsulation command. Why Other Options Are Wrong: 1 only or 1,3,4: Includes VTP, which is not a trunk encapsulation protocol. 3 only: Excludes ISL, which has historically been used for trunk encapsulation. 2 and 3 only: Item 2 is not part of the presented list in the prompt and is irrelevant here. Common Pitfalls: Assuming VTP configures or negotiates the trunk encapsulation; it does not. Confusing DTP (Dynamic Trunking Protocol) with VTP; DTP negotiates trunk formation, not encapsulation. Final Answer: 3 and 4

Question 17

Technology that reduces broadcast domain size In a switched network, which technology is specifically used to reduce the size of broadcast domains by logically segmenting Layer 2 networks into separate groups?

Accepted Answer

Introduction / Context: Broadcast traffic (for example ARP) is confined to broadcast domains. In large Layer 2 networks, excessive broadcasts can degrade performance and pose security risks. VLANs allow administrators to segment a physical switch into multiple logical networks, each with its own broadcast domain, improving performance and security posture. Given Data / Assumptions: The environment uses Ethernet switching. Goal: Reduce the scope of broadcasts. We are looking for the overarching technology, not just the tagging standard or loop prevention. Concept / Approach: VLANs (Virtual LANs) define logical Layer 2 segments. Each VLAN forms its own broadcast domain; broadcasts are not flooded across VLAN boundaries. Inter-VLAN communication requires Layer 3 routing, which provides control and filtering between segments. Standards like 802.1Q define how VLAN tags are carried over trunks, but the reduction in broadcast domain size is achieved by the VLAN segmentation itself. Step-by-Step Solution: Define VLANs aligned to departments or functions.Assign ports to VLANs so that hosts share only necessary broadcast scope.Use trunks between switches to carry multiple VLANs.Provide inter-VLAN routing where needed for cross-VLAN communication. Verification / Alternative check: Monitor broadcast counters per VLAN with switch commands; you will see broadcasts are contained within each VLAN, not across the entire campus switch fabric. Why Other Options Are Wrong: ISL and 802.1Q: Encapsulation/standard for tagging; they enable trunks but do not themselves define the segmentation concept. STP: Prevents loops; it does not reduce broadcast domain size. Port mirroring: Diagnostic feature; unrelated to broadcast domains. Common Pitfalls: Confusing the tagging method (802.1Q) with the segmentation concept (VLANs). Assuming STP limits broadcast domains; it only influences topology and forwarding states. Final Answer: VLANs

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