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Question 941Question →

A network engineer deploys lightweight access points (LAPs) at a remote branch office connected over a WAN to a centralized Wireless LAN Controller (WLC). During a WAN outage, clients connected to APs in Local mode lose network connectivity, while clients connected to APs configured in FlexConnect mode with local switching retain local network access. Which operational characteristic of Local mode APs accounts for this behavior?

Show answer & explanation

Answer: Local mode APs encapsulate all client data traffic within CAPWAP data tunnels to be switched centrally by the WLC.

Answer

Local mode APs encapsulate all client data traffic within CAPWAP data tunnels to be switched centrally by the WLC.
In Cisco Centralized WLAN architectures, APs operating in Local mode encapsulate all client user traffic within CAPWAP data tunnels and forward it to the Wireless LAN Controller (WLC) for centralized processing and 802.3 Ethernet conversion. Consequently, if WAN connectivity to the central WLC is lost, Local mode APs cannot process or forward client traffic. In contrast, FlexConnect mode with local switching allows the AP to perform frame translation and switch client traffic directly onto the local branch switch, keeping local resources accessible during a WLC outage.

Step-by-Step Solution

1
Analyze the operational behavior of Local mode in a Cisco Centralized WLAN architecture.
Local mode lightweight APs send both CAPWAP control and CAPWAP data packets back to the central WLC.
Centralized switching requires all 802.11 frames to be encapsulated in CAPWAP and sent to the WLC, where 802.11 to 802.3 frame conversion occurs.
2
Evaluate the impact of WAN failure and loss of WLC reachability on Local mode APs.
Since data switching depends on reaching the WLC, losing WLC connectivity prevents Local mode APs from forwarding client traffic.
Local mode APs cannot locally bridge client traffic to the branch switch infrastructure.
3
Compare with FlexConnect mode configured for local switching.
FlexConnect APs perform 802.11 to 802.3 frame translation locally at the branch level, allowing traffic to continue flowing locally even when WLC connectivity is lost.
FlexConnect separates local data path switching from centralized controller management.

Key Concept

Cisco Lightweight Access Point Modes (Local vs. FlexConnect) and CAPWAP Data Tunneling
Question 942Question →

A system architect is migrating a software-defined branch office infrastructure from hosted hypervisors (Type 2) to bare-metal hypervisors (Type 1). During performance baseline testing, the team observes significantly reduced network frame handling latency and lower host CPU overhead on the bare-metal architecture. Which architectural characteristic of Type 1 hypervisors accounts for this performance improvement?

Show answer & explanation

Answer: The hypervisor manages physical hardware resources directly without passing kernel calls through a host operating system layer.

Answer

The hypervisor manages physical hardware resources directly without passing kernel calls through a host operating system layer.
Type 1 (bare-metal) hypervisors run directly on the host server hardware with direct access to hardware resources such as CPU, memory, and physical NICs. Because there is no general-purpose host operating system running underneath, virtual machine I/O operations and virtual switch frame handling do not suffer from extra OS kernel translation steps or scheduler contention, resulting in significantly lower latency and CPU overhead.

Step-by-Step Solution

1
Analyze the architecture of Type 1 (bare-metal) vs. Type 2 (hosted) hypervisors.
Type 1 hypervisors sit directly on physical server hardware, whereas Type 2 hypervisors execute on top of an existing host operating system.
Understanding the hardware interface boundary is critical for determining performance overhead.
2
Evaluate the impact of host OS elimination on packet processing and resource scheduling.
By eliminating the host OS layer, Type 1 hypervisors gain direct control over physical NIC drivers and CPU scheduling, reducing I/O latency and CPU context-switching overhead.
Direct hardware interaction removes intermediate kernel context switches and resource competition.
3
Match the observed performance efficiency to the underlying architectural mechanism.
Direct management of hardware resources without a host OS translation layer explains the lower latency and reduced CPU utilization.
This direct hardware access is the primary architectural differentiator of bare-metal virtualization.

Key Concept

Type 1 vs Type 2 Hypervisor Architecture
Question 943Question →

Match each IPv6 address type on the left with its corresponding reserved prefix range on the right. Which pairs correctly match each IPv6 address scope to its standard IPv6 prefix?

Click a left item, then click its matching right item

Items

Global Unicast Address
Link-Local Address
Unique Local Address
Multicast Address

Matches

Show answer & explanation

Answer

Global Unicast Address pairs with 2000::/3, Link-Local Address pairs with fe80::/10, Unique Local Address pairs with fc00::/7, and Multicast Address pairs with ff00::/8.
Each standard IPv6 address scope is assigned a dedicated prefix block by IANA and RFC 4291: Global Unicast uses 2000::/3 for public Internet traffic, Link-Local uses fe80::/10 for interface communication on the same link, Unique Local uses fc00::/7 for internal site routing, and Multicast uses ff00::/8 for group delivery.

Step-by-Step Solution

1
Identify the reserved prefix block for IPv6 Global Unicast addresses.
Global Unicast Address maps to 2000::/3.
Global Unicast IPv6 addresses are defined by RFC 4291 as starting in the 2000::/3 prefix range (2000:: through 3FFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF).
2
Identify the reserved prefix block for IPv6 Link-Local addresses.
Link-Local Address maps to fe80::/10.
IPv6 link-local addresses use the prefix fe80::/10, which covers fe80:: through febf:ffff:ffff:ffff:ffff:ffff:ffff:ffff.
3
Identify the reserved prefix block for IPv6 Unique Local addresses (ULA).
Unique Local Address maps to fc00::/7.
Unique Local IPv6 addresses are analogous to IPv4 private addresses and start with the fc00::/7 block (fc00:: through fdff:ffff:ffff:ffff:ffff:ffff:ffff:ffff).
4
Identify the reserved prefix block for IPv6 Multicast addresses.
Multicast Address maps to ff00::/8.
All IPv6 multicast addresses begin with the prefix byte ff00::/8.

Key Concept

IPv6 Address Types and Reserved Prefixes
Question 944Question →

Two Cisco Catalyst switches, SW1 and SW2, are connected via their GigabitEthernet0/1 interfaces. SW1 is configured with `switchport mode dynamic desirable`, `switchport trunk native vlan 20`, and `switchport trunk allowed vlan 10,20,30`. SW2 is configured with default DTP settings (`switchport mode dynamic auto`), `switchport trunk native vlan 1`, and `switchport trunk allowed vlan 10,20,40`. Which of the following statements accurately describe the operational status and traffic behavior across this interswitch link? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: The link operational state becomes an 802.1Q trunk because Dynamic Trunking Protocol (DTP) dynamic desirable mode on SW1 successfully negotiates with dynamic auto mode on SW2.; Traffic transmitted across the link for VLAN 10 is tagged with an explicit 4-byte 802.1Q header containing VLAN ID 10.

Answer

The operational state becomes an 802.1Q trunk due to successful DTP negotiation between dynamic desirable and dynamic auto modes, and traffic for VLAN 10 will carry a standard 4-byte 802.1Q tag header across the trunk link.
The combination of dynamic desirable on one end and dynamic auto on the other causes DTP to successfully negotiate an operational 802.1Q trunk. For any tagged VLAN allowed across the link that is not designated as native (such as VLAN 10), 802.1Q inserts a standard 4-byte field into the Ethernet frame header.

Step-by-Step Solution

1
Analyze Dynamic Trunking Protocol (DTP) operational mode interaction.
SW1 (dynamic desirable) actively sends DTP frames to negotiate trunking. SW2 (dynamic auto) listens and agrees to trunk, resulting in an operational trunk link.
Dynamic desirable + dynamic auto always yields an operational trunk link.
2
Evaluate IEEE 802.1Q tagging behavior for non-native allowed VLANs.
VLAN 10 is allowed on both sides and is non-native for both switches. Frames belonging to VLAN 10 are inserted with an explicit 4-byte 802.1Q header containing the VLAN ID.
Standard 802.1Q trunking tags all non-native VLAN traffic.
3
Evaluate native VLAN processing during mismatches.
SW1 sends VLAN 20 untagged (its native VLAN), while SW2 expects VLAN 1 untagged. Neither switch automatically tags its native VLAN unless globally configured via 'vlan dot1q tag native'. Mismatched native VLAN configuration leads to STP PVID inconsistencies, but does not alter local untagged frame generation.
Native VLAN configuration dictates local untagged frame transmission rules independently on each side.

Key Concept

802.1Q Interswitch Trunking Negotiation and Frame Tagging Mechanics
Estimated Time:2m 0s
Question 945Question →

An administrator is auditing a dual-stack network segment where hosts use Stateless Address Autoconfiguration (SLAAC) with EUI-64 to derive their 64-bit interface identifiers. A workstation with the Burned-In MAC address `34-E6-D7-89-0A-1B` sends a Router Solicitation message. What is the correctly formatted IPv6 Link-Local address generated by this interface?

Show answer & explanation

Answer: FE80::36E6:D7FF:FE89:0A1B

Answer

The correct IPv6 Link-Local address is FE80::36E6:D7FF:FE89:0A1B.
To construct an IPv6 EUI-64 interface identifier from a 48-bit MAC address (34-E6-D7-89-0A-1B), the 7th bit (Universal/Local bit) of the first byte must be inverted, and the 16-bit hex value FFFE must be inserted between the third and fourth bytes. The first byte 0x34 is 0011 0100 in binary; flipping the 7th bit produces 0011 0110 (0x36). Inserting FFFE into 36-E6-D7 and 89-0A-1B yields the interface ID 36E6:D7FF:FE89:0A1B. Appending this to the FE80:: link-local prefix forms FE80::36E6:D7FF:FE89:0A1B.

Step-by-Step Solution

1
Identify the IPv6 Link-Local prefix.
Link-Local addresses begin with FE80::/10 (typically formatted as FE80::/64 for host interfaces).
SLAAC link-local autoconfiguration uses FE80::/64 as the default prefix network segment.
2
Convert the first byte of the MAC address to binary and invert the 7th bit (Universal/Local bit).
The first byte 0x34 in binary is 0011 0100. Inverting the 7th bit (the 2nd least significant bit) changes 0011 0100 to 0011 0110, which is 0x36 in hexadecimal.
IEEE EUI-64 specification requires flipping the U/L bit to indicate a universally administered address modified for EUI-64 usage.
3
Split the modified MAC address into two 24-bit halves and insert FFFE in the middle.
The modified MAC `36-E6-D7-89-0A-1B` becomes `36-E6-D7` and `89-0A-1B`. Inserting `FF-FE` yields `36E6:D7FF:FE89:0A1B` in standard IPv6 hexadecimal notation.
Expanding a 48-bit MAC address into a 64-bit EUI-64 interface identifier requires inserting the 16-bit value FFFE at the center.
4
Combine the link-local prefix with the derived 64-bit EUI-64 interface identifier.
FE80:: + 36E6:D7FF:FE89:0A1B = FE80::36E6:D7FF:FE89:0A1B.
The complete 128-bit link-local address consists of the 64-bit FE80:: prefix and the 64-bit interface ID.

Key Concept

EUI-64 Interface Identifier Derivation for IPv6 Link-Local Addresses
Estimated Time:1m 30s
Question 946Question →

A network administrator is allocated the IPv6 prefix block 2001:db8:5678:a000::/522001:\text{db8}:5678:\text{a000}::/52 for an enterprise deployment. Which two IPv6 addresses belong to valid subnets within this assigned prefix block? (Select two.)

Select all that apply

Show answer & explanation

Answer: 2001:db8:5678:a4f0:1::1/64; 2001:db8:5678:ab00::1/64

Answer

The correct IPv6 addresses are 2001:db8:5678:a4f0:1::1/64 and 2001:db8:5678:ab00::1/64 because their fourth hextet values (a4f0 and ab00) lie within the range a000 to afff specified by the /52 prefix boundary.
The correct options are the addresses featuring 'a4f0' and 'ab00' as their fourth hextet. A /52 prefix locks the first 52 bits of the IPv6 address. The first three 16-bit hextets supply 48 bits, leaving 4 bits to lock the first hex digit of the fourth hextet. Since 'a' represents binary 1010 across bits 49–52, any valid address under this prefix must have a fourth hextet starting with 'a' (ranging from a000 to afff).

Step-by-Step Solution

1
Analyze the assigned IPv6 prefix length and identify hex nibble boundaries.
The prefix 2001:db8:5678:a000::/522001:\text{db8}:5678:\text{a000}::/52 has 5252 fixed network bits. Each hex character (nibble) represents 44 bits. The first three hextets (2001:db8:56782001:\text{db8}:5678) account for 4848 bits (3×163 \times 16). The remaining 44 network bits (52−48=452 - 48 = 4) lock the first nibble of the fourth hextet.
Determining where the prefix boundary falls inside the fourth hextet allows precise identification of valid subnet ranges.
2
Calculate the valid range of values for the fourth hextet.
The hex character ’a’\text{'a'} corresponds to binary 10101010. Since the first 44 bits of the fourth hextet must remain 10101010, the fourth hextet can range from a000\text{a000} (1010 0000 0000 000021010\ 0000\ 0000\ 0000_2) to afff\text{afff} (1010 1111 1111 111121010\ 1111\ 1111\ 1111_2).
Any valid subnet address must have a fourth hextet between a000 and afff.
3
Evaluate each candidate address against the calculated fourth hextet range.
The addresses containing 'a4f0' and 'ab00' in their fourth hextet are within the range a000-afff. The address with 'b000' starts the next block (2001:db8:5678:b000::/522001:\text{db8}:5678:\text{b000}::/52), and 'a00' expands to '0a00', which falls below 'a000'.
Only addresses matching the leading nibble 'a' in the fourth hextet belong to the designated /52 block.

Key Concept

IPv6 Prefix Length Boundaries and Hexadecimal Subnet Range Calculation
Question 947Question →

A network administrator is designing the transport transport layer profile for an enterprise network management system. The system requires a stateless transport mechanism for high-frequency, low-latency telemetry collection where occasional packet loss is tolerable, alongside a stateful transport mechanism for secure interactive router configuration sessions. Which two characteristics accurately describe the transport layer protocols selected for these respective roles? (Select two.)

Select all that apply

Show answer & explanation

Answer: User Datagram Protocol (UDP) utilizes a fixed 8-byte header to minimize processing overhead for rapid telemetry collection.; Transmission Control Protocol (TCP) incorporates a dynamic window size field within its baseline 20-byte header to perform flow control during configuration sessions.

Answer

UDP employs a streamlined 8-byte header to eliminate protocol overhead for real-time telemetry, while TCP utilizes a 20-byte baseline header with a dynamic Window Size field to manage flow control for interactive administrative sessions.
The selection of UDP for telemetry is supported by its minimal 8-byte fixed header length, which reduces processing and bandwidth overhead. The selection of TCP for interactive router management is supported by its standard 20-byte header containing the Window Size field, enabling dynamic sliding-window flow control to prevent receiver buffer exhaustion.

Step-by-Step Solution

1
Analyze transport protocol requirements for low-latency telemetry data.
UDP is chosen because it is connectionless and introduces minimal overhead.
The 8-byte UDP header contains only four fields, avoiding state maintenance and handshake delays.
2
Analyze transport protocol requirements for interactive administrative sessions.
TCP is chosen to guarantee reliable, ordered delivery and flow control.
The baseline 20-byte TCP header contains fields for sequencing, acknowledgments, and window size adjustment.
3
Evaluate the option choices against protocol header structures and operational behavior.
The statements describing the 8-byte UDP header and the TCP 20-byte header with window size flow control are accurate, whereas claims of UDP sequence tracking and handshake-free TCP data delivery are false.
UDP lacks sequence fields in its header, and TCP mandates session initialization via a three-way handshake prior to payload transfer.

Key Concept

TCP and UDP Header Structure and Operational Mechanics
Question 948Question →

A network administrator configures a Cisco Catalyst switch with a new VLAN and assigns an access port using the following command sequence:

Switch(config)# vlan 50
Switch(config-vlan)# name HR_Data
Switch(config-vlan)# exit
Switch(config)# interface fastEthernet 0/15
Switch(config-if)# switchport mode access
Switch(config-if)# switchport access vlan 50

Several weeks later, another engineer executes the command 'no vlan 50' in global configuration mode to remove VLAN 50 from the switch. What is the immediate operational state and forwarding behavior of port FastEthernet 0/15 after VLAN 50 is deleted?

Show answer & explanation

Answer: The port remains configured for VLAN 50, but becomes inactive and drops all incoming and outgoing frames.

Answer

The port remains configured for VLAN 50, but becomes inactive and drops all incoming and outgoing frames.
When a VLAN is deleted from a Cisco switch using the global configuration command 'no vlan <id>', the switch does not modify interface-level configuration commands. Interfaces previously assigned to that VLAN retain their 'switchport access vlan <id>' setting. However, because the target VLAN no longer exists in the Layer 2 VLAN table, the switchport becomes inactive and cannot forward frames until the VLAN is re-created globally or the port is reassigned to an existing active VLAN.

Step-by-Step Solution

1
Analyze interface configuration retention upon VLAN deletion in Cisco IOS.
Removing a VLAN globally with 'no vlan <id>' removes the VLAN entry from the VLAN database (vlan.dat), but does not alter the running configuration of interfaces configured with 'switchport access vlan <id>'.
Interface configuration commands and global VLAN database definitions operate independently.
2
Determine the operational forwarding state of an interface assigned to a non-existent VLAN.
Because the assigned access VLAN no longer exists in Layer 2 forwarding tables, the switchport becomes inactive and fails to forward ingress or egress traffic for attached hosts.
A switchport cannot forward Layer 2 frames unless its configured access VLAN actively exists in the switch's VLAN database.

Key Concept

Access Port Behavior upon VLAN Deletion
Question 949Question →

Match each virtualization component on the left with its corresponding primary function or definition on the right.

Click a left item, then click its matching right item

Items

Hypervisor
Virtual Switch (vSwitch)
Virtual Network Interface Card (vNIC)
Virtual Machine (VM)

Matches

Show answer & explanation

Answer

Hypervisor matches with the software layer managing host hardware resources; Virtual Switch matches with the software entity performing Layer 2 frame forwarding; Virtual Network Interface Card matches with the software-based network adapter presented to a guest OS; Virtual Machine matches with the isolated software container executing a guest OS.
Each virtualized component serves a distinct role in network and hardware virtualization: the hypervisor manages underlying hardware allocation, the vSwitch handles software-based Layer 2 frame forwarding, the vNIC functions as the software network adapter for guest OS connection, and the VM is the hosted guest compute instance.

Step-by-Step Solution

1
Identify the role of the Hypervisor
The hypervisor controls and allocates physical hardware resources (CPU, RAM, storage) to virtual environments.
It acts as the core virtualization engine enabling multi-tenancy on physical hardware.
2
Identify the role of the Virtual Switch (vSwitch)
The vSwitch manages Layer 2 forwarding within the hypervisor host.
It connects virtual interfaces to each other and bridges virtual network traffic to physical network interface cards (pNICs).
3
Identify the role of the Virtual Network Interface Card (vNIC)
The vNIC acts as the guest system's virtual Ethernet interface.
It binds to a VM and plugs virtually into a port on a vSwitch.
4
Identify the role of the Virtual Machine (VM)
The VM is the virtualized compute instance.
It operates as an independent operating system container hosted by the hypervisor.

Key Concept

Virtualization Abstraction Components and Functions
Question 950Question →

Match each network topology architecture model or functional layer on the left to its corresponding design trait and operational responsibility on the right.

Click a left item, then click its matching right item

Items

Collapsed Core Architecture Layer
Three-Tier Core Layer
Three-Tier Distribution Layer
Data Center Spine Layer (Clos)

Matches

Show answer & explanation

Answer

Collapsed Core Architecture Layer matches the description combining core transport and policy enforcement into a single switch pair. Three-Tier Core Layer matches the description providing high-speed transport without CPU-intensive packet inspection or ACL filtering. Three-Tier Distribution Layer matches the description aggregating Access switches, acting as the L2/L3 boundary, and enforcing security policies. Data Center Spine Layer matches the description functioning as a high-bandwidth IP fabric backbone with predictable single-hop latency.
Each architecture layer is uniquely optimized for its operational domain: Collapsed Core combines distribution and core functions for smaller networks; Three-Tier Core optimizes raw forwarding speed without packet filtering; Three-Tier Distribution acts as the control boundary for VLANs, security policies, and routing aggregation; Spine-Leaf Spine nodes provide predictable, non-blocking single-hop transport between all leaf switches.

Step-by-Step Solution

1
Analyze the functional responsibilities of campus network layers.
Identify that the Core layer focuses exclusively on transport speed, while the Distribution layer handles routing boundaries, ACLs, and policy enforcement.
Separation of duties in campus designs prevents performance bottlenecks on the core backbone.
2
Evaluate the Collapsed Core model.
Recognize that Collapsed Core integrates core switching and distribution policies into one physical tier, suited for medium enterprise designs.
Combining layers lowers equipment cost while retaining high availability.
3
Examine data center Spine-Leaf (Clos) architectural dynamics.
Distinguish that Spine switches form a full mesh fabric with Leaf switches to optimize east-west server traffic with deterministic latency.
Spine switches do not connect to each other; they strictly interconnect leaf nodes across a non-blocking Layer 3 fabric.

Key Concept

Network Architectural Layer Functional Responsibilities and Design Trade-offs
Question 951Question →

A network administrator is reviewing bandwidth efficiency for application traffic traversing a low-bandwidth WAN link. Which statement accurately compares the baseline header size overhead between Transmission Control Protocol (TCP) and User Datagram Protocol (UDP)?

Show answer & explanation

Answer: TCP requires a 20-byte minimum header to accommodate reliability tracking fields, whereas UDP uses an 8-byte header to minimize transmission overhead.

Answer

TCP requires a 20-byte minimum header to accommodate reliability tracking fields, whereas UDP uses an 8-byte header to minimize transmission overhead.
The option identifying TCP's 20-byte minimum header and UDP's 8-byte fixed header is correct because TCP must carry fields for flow control, error recovery, and sequencing, whereas UDP only carries basic addressing, length, and checksum information.

Step-by-Step Solution

1
Analyze TCP header requirements
TCP is a connection-oriented, reliable protocol that requires fields for Source/Destination Ports, Sequence Number, Acknowledgment Number, Data Offset, Control Flags, Window Size, Checksum, and Urgent Pointer, consuming 20 bytes minimum.
Reliability mechanisms demand additional header fields.
2
Analyze UDP header requirements
UDP is a connectionless, best-effort protocol containing only Source Port, Destination Port, Length, and Checksum fields, totaling 8 bytes.
Absence of sequencing and flow control allows for minimal header overhead.
3
Compare protocol header sizes
TCP headers are at least 20 bytes, while UDP headers are fixed at 8 bytes.
This structural difference directly reflects their performance and reliability tradeoffs.

Key Concept

TCP vs UDP Header Size and Overhead Comparison
Question 952Question →

An engineer executes the `show interfaces trunk` command on a Cisco Catalyst switch interface GigabitEthernet0/2 and observes the following output:

text
Port Vlans allowed on trunk
Gi0/2 10,20,30

Port Vlans allowed and active in management domain
Gi0/2 10,20

Port Vlans in spanning tree forwarding state and not pruned
Gi0/2 10

Which condition explains why VLAN 30 is listed as allowed on the trunk, but is missing from the list of active VLANs in the management domain?

Show answer & explanation

Answer: VLAN 30 has not been created in the local VLAN database of the switch.

Answer

VLAN 30 has not been created in the local VLAN database of the switch.
In Cisco IOS, `show interfaces trunk` divides VLAN status into three operational categories. The first list shows administratively allowed VLANs (`switchport trunk allowed vlan`). The second list shows VLANs that are both administratively allowed AND present in the local switch VLAN database (`vlan <id>`). Because VLAN 30 appears in the first list but not the second, VLAN 30 has not been defined globally in the local switch VLAN database.

Step-by-Step Solution

1
Analyze the 'Vlans allowed on trunk' output section
VLANs 10, 20, and 30 are configured under the interface `switchport trunk allowed vlan` command.
This section displays the administrative list of allowed VLANs configured on the interface.
2
Analyze the 'Vlans allowed and active in management domain' section
VLAN 30 is absent from this list.
To be active in the management domain, a VLAN must exist in the switch's local VLAN database (`vlan 30`) and not be in a suspended state.
3
Deduce the root cause of the missing VLAN entry
VLAN 30 has not been created using the `vlan 30` global configuration command on the local switch.
Configuring a VLAN in the interface allowed list without creating the VLAN in global configuration prevents the switch from tagging or forwarding frames for that VLAN.

Key Concept

802.1Q Trunk Allowed vs Active VLAN Operation
Question 953Question →

Which two statements correctly describe IEEE 802.1Q trunking operational behavior on Cisco Catalyst switches? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: By default, Ethernet frames belonging to the configured native VLAN are transmitted across the trunk link without an 802.1Q header tag.; An 802.1Q header inserts 4 bytes into the Ethernet frame, which includes a 12-bit field dedicated to identifying the VLAN ID.

Answer

IEEE 802.1Q sends native VLAN traffic untagged across trunk links by default, and encapsulates tagged frames using a 4-byte header containing a 12-bit VLAN ID field.
IEEE 802.1Q trunking forwards native VLAN frames untagged by default. For all other VLANs, it inserts a 4-byte tag into the Ethernet header which incorporates a 12-bit VLAN Identifier.

Step-by-Step Solution

1
Identify standard 802.1Q frame structure and tagging rules.
Tagged frames receive a 4-byte tag containing a 12-bit VLAN ID, while frames on the native VLAN are forwarded untagged across the link by default.
802.1Q specifies untagged frame delivery for native VLAN traffic to ensure compatibility.
2
Examine the impact of configuring PortFast on switch-to-switch links.
PortFast skips STP listening and learning states, which can cause temporary Layer 2 loops if configured on interswitch trunk ports.
PortFast is designed strictly for access ports connected to end-user devices.
3
Analyze switch behavior when a native VLAN mismatch occurs across a trunk.
Traffic leaks across VLAN boundaries and CDP/STP generates warning logs, but the switch keeps the trunk operational rather than disabling the port.
Cisco switches flag PVID inconsistencies without automatically placing the interface into an err-disabled state.

Key Concept

802.1Q Frame Tagging and Trunk Operations
Estimated Time:1m 0s
Question 954Question →

A network engineer is deploying new infrastructure across a multi-site enterprise network. Match each network component on the left to its primary operational function on the right.

Click a left item, then click its matching right item

Items

Router
Next-Generation Firewall (NGFW)
Wireless LAN Controller (WLC)
Layer 2 Switch

Matches

Show answer & explanation

Answer

Router matches with evaluating Layer 3 IP headers to forward packets between subnets. Next-Generation Firewall (NGFW) matches with stateful packet filtering, deep packet inspection, and threat prevention. Wireless LAN Controller (WLC) matches with centralizing radio resource management, AP provisioning, and mobility. Layer 2 Switch matches with forwarding frames within the same local network segment based on destination MAC addresses.
Each component is mapped to its core operational role: Routers perform Layer 3 path determination between distinct IP subnets; Next-Generation Firewalls conduct stateful security filtering and deep packet inspection; Wireless LAN Controllers manage and provision lightweight access points centrally; and Layer 2 Switches perform MAC address-based frame switching within a local broadcast domain.

Step-by-Step Solution

1
Identify the primary operating OSI layer and function of a Router.
Routers operate at Layer 3 (Network layer), making forwarding decisions using IP addresses to route packets between different networks.
Routing across subnet boundaries requires network layer addressing and broadcast domain separation.
2
Identify the distinct security enforcement capabilities of an NGFW.
NGFWs inspect traffic statefully across multiple OSI layers, enforcing security policies, IPS, and application awareness.
Firewalls protect network perimeters by filtering unauthorized or malicious traffic.
3
Determine the management role of a Wireless LAN Controller (WLC).
WLCs provide centralized management for lightweight access points, handling RF configuration, roaming, and security policies.
Split-MAC wireless architectures centralize control-plane functions on the WLC.
4
Determine the forwarding behavior of a Layer 2 Switch.
Layer 2 switches inspect Ethernet frames and use the MAC address table to forward traffic within a single broadcast domain.
Switches handle local network frame switching at Layer 2 without modifying IP headers.

Key Concept

Network Components Roles and Functions
Question 955Question →

A network engineer is configuring a Cisco router interface with the command `ipv6 address 2001:db8:cafe:100::/64 eui-64`. The burn-in MAC address of the interface is `1866.DA12.3456`. Based on the IEEE EUI-64 process, which IPv6 global unicast address will be dynamically assigned to this interface?

Show answer & explanation

Answer: 2001:db8:cafe:100:1a66:daff:fe12:3456

Answer

The dynamically generated IPv6 address assigned to the interface is 2001:db8:cafe:100:1a66:daff:fe12:3456.
The EUI-64 creation process takes the 48-bit MAC address (1866.DA12.3456), splits it into two 24-bit pieces, inserts FFFE in the middle (1866:DAFF:FE12:3456), and flips the 7th bit of the first byte (0x18 = 0001 1000 becomes 0x1A = 0001 1010). Appending this 64-bit interface ID to the specified 2001:db8:cafe:100::/64 prefix yields 2001:db8:cafe:100:1a66:daff:fe12:3456.

Step-by-Step Solution

1
Split MAC address into two equal 24-bit halves
Left half: 18-66-DA, Right half: 12-34-56
EUI-64 requires inserting a 16-bit hex value (FFFE) into the center of the 48-bit MAC address.
2
Insert FFFE between the two 24-bit halves
1866:DAFF:FE12:3456
This expands the 48-bit MAC address to a 64-bit interface identifier structure.
3
Invert the 7th bit (Universal/Local bit) of the first byte
First byte 0x18 (0001 1000 in binary) becomes 0x1A (0001 1010 in binary), making the interface ID 1a66:daff:fe12:3456
The IEEE EUI-64 standard specifies flipping the U/L bit (7th bit from left) to indicate whether the address is universally or locally administered.
4
Combine the /64 IPv6 prefix with the modified 64-bit interface ID
2001:db8:cafe:100:1a66:daff:fe12:3456
Concatenating the prefix 2001:db8:cafe:100::/64 with the EUI-64 interface ID creates the full 128-bit IPv6 global unicast address.

Key Concept

EUI-64 Interface Identifier Generation
Estimated Time:1m 30s
Question 956Question →

An engineer captures traffic on a point-to-point trunk link between two switches. Switch-1 is configured with `switchport trunk native vlan 10`, while Switch-2 is configured with `switchport trunk native vlan 20`. When Switch-1 transmits untagged frames originating from VLAN 10 across the trunk link, how does Switch-2 process these frames upon ingress, and what operational issue occurs?

Show answer & explanation

Answer: Switch-2 assigns the received untagged frames to VLAN 20, resulting in cross-VLAN traffic leakage, while CDP continuously reports a native VLAN mismatch.

Answer

Switch-2 assigns the received untagged frames to VLAN 20, resulting in cross-VLAN traffic leakage, while CDP continuously reports a native VLAN mismatch.
Under 802.1Q trunking rules, native VLAN frames are transmitted untagged. When Switch-1 forwards VLAN 10 frames across the trunk without an 802.1Q tag, Switch-2 accepts the untagged frames and assigns them to its own configured native VLAN (VLAN 20). This leads to unintended cross-VLAN traffic leakage between VLAN 10 and VLAN 20. Additionally, CDP detects this discrepancy by exchanging native VLAN details in TLVs and regularly issues syslog warnings.

Step-by-Step Solution

1
Analyze Switch-1 egress processing for native VLAN 10
Frames originating from VLAN 10 are transmitted untagged across the 802.1Q trunk because VLAN 10 matches Switch-1's native VLAN configuration.
According to IEEE 802.1Q specifications, frames belonging to the configured native VLAN are sent across a trunk link without inserting a 4-byte VLAN tag header.
2
Analyze Switch-2 ingress processing for untagged frames
Switch-2 receives the untagged frames and maps them directly into its own native VLAN, which is VLAN 20.
When an 802.1Q trunk interface receives an untagged frame, it automatically assigns that frame to whichever VLAN is designated as native on that local receiving interface.
3
Determine operational impact and diagnostic behavior
Cross-VLAN traffic leakage occurs between VLAN 10 on Switch-1 and VLAN 20 on Switch-2, and CDP logs native VLAN mismatch notifications.
A native VLAN mismatch breaks logical isolation between different VLANs and triggers warning messages via CDP native VLAN TLV exchange.

Key Concept

802.1Q Native VLAN Ingress Processing and Mismatch Behavior
Estimated Time:2m 0s
Question 957Question →

A network administrator is analyzing Cisco IOS switch interface outputs to resolve network degradation. Match each interface status combination or error counter condition on the left to its corresponding primary root cause on the right.

Click a left item, then click its matching right item

Items

Interface state: FastEthernet0/1 is up, line protocol is down
Interface state: FastEthernet0/2 is administratively down, line protocol is down
Interface statistics: High count of late collisions on an interface operating in full-duplex
Interface statistics: Increasing count of runts accompanied by CRC errors

Matches

Show answer & explanation

Answer

FastEthernet0/1 up/down matches Layer 2 encapsulation mismatch, keepalive failure, or missing framing. FastEthernet0/2 administratively down matches interface manually disabled via the shutdown command. High count of late collisions matches a duplex mismatch with local full-duplex and remote half-duplex. Increasing runts with CRC errors matches physical cable noise, EMI, or collision fragments creating sub-64 byte frames.
Each interface state and counter statistic accurately aligns with its underlying physical or data-link layer cause: 'up/down' denotes Layer 2 framing/keepalive failure, 'administratively down' represents a software shutdown command, late collisions stem from a duplex mismatch between full-duplex and half-duplex endpoints, and runts with CRC errors signify frame corruption under 64 bytes due to physical noise or collisions.

Step-by-Step Solution

1
Analyze interface operational states for Layer 1 vs Layer 2 status
Determine that 'up, line protocol down' indicates physical carrier presence with data-link failure, whereas 'administratively down' represents a software-disabled port.
Cisco IOS separates physical layer link carrier status from data-link protocol keepalive and framing verification.
2
Evaluate CLI error counter symptoms
Associate late collisions with a duplex mismatch scenario and runts paired with CRC errors with physical noise or truncated collision fragments.
Late collisions indicate transmission collisions occurring past the first 64 bytes due to full-duplex ignoring carrier sense, while runts reflect corrupted frame fragments below the minimum Ethernet frame length.

Key Concept

Cisco IOS interface status states and error counter interpretation
Question 958Question →

A network architect is implementing Variable Length Subnet Masking (VLSM) for an enterprise branch using the assigned summary prefix 172.20.0.0/19172.20.0.0/19. Four subnets must be allocated sequentially from the lowest available IP address of the block to support the following minimum host requirements:

- Location A: 1,000 usable hosts
- Location B: 480 usable hosts
- Location C: 250 usable hosts
- Location D: 120 usable hosts

Each subnet must be sized using the smallest possible prefix length to satisfy its host requirement. After completing these four allocations in order (Location A, then B, then C, then D), what is the maximum number of usable host IPv4 addresses that can be accommodated in the single largest contiguous unallocated subnet block remaining in the 172.20.0.0/19172.20.0.0/19 summary range?

Show answer & explanation

Answer: 4094

Answer

The maximum number of usable host addresses in the single largest contiguous unallocated subnet block remaining is 4094.
The base block 172.20.0.0/19172.20.0.0/19 contains 213=81922^{13} = 8192 total IP addresses (ranging from 172.20.0.0172.20.0.0 to 172.20.31.255172.20.31.255). Allocating for Locations A (/22/22, 1024 IPs), B (/23/23, 512 IPs), C (/24/24, 256 IPs), and D (/25/25, 128 IPs) uses addresses 172.20.0.0172.20.0.0 through 172.20.7.127172.20.7.127. The remaining space (172.20.7.128172.20.7.128 to 172.20.31.255172.20.31.255) decomposes into three valid CIDR subnets: 172.20.7.128/25172.20.7.128/25 (128 IPs), 172.20.8.0/21172.20.8.0/21 (2048 IPs), and 172.20.16.0/20172.20.16.0/20 (4096 IPs). The largest single contiguous subnet is 172.20.16.0/20172.20.16.0/20, which accommodates 212−2=40942^{12} - 2 = 4094 usable host addresses.

Step-by-Step Solution

1
Calculate required prefix lengths and allocated address ranges for each location sequentially starting at 172.20.0.0
Location A (1000 hosts) requires /22 (1024 total IPs: 172.20.0.0 - 172.20.3.255). Location B (480 hosts) requires /23 (512 total IPs: 172.20.4.0 - 172.20.5.255). Location C (250 hosts) requires /24 (256 total IPs: 172.20.6.0 - 172.20.6.255). Location D (120 hosts) requires /25 (128 total IPs: 172.20.7.0 - 172.20.7.127).
Each subnet host capacity is calculated using 2^h - 2, where h is the host bits. Minimum prefix blocks must align on natural network boundaries.
2
Analyze the remaining unallocated address range within the 172.20.0.0/19 block
The total /19 block spans 172.20.0.0 to 172.20.31.255 (8192 total IPs). Address space used so far is 172.20.0.0 through 172.20.7.127 (1920 IPs). Unallocated range is 172.20.7.128 to 172.20.31.255.
Subtracting allocated IP space from the base summary block isolates the remaining contiguous unassigned addresses.
3
Partition remaining unallocated space into standard summary subnets and find the largest block
Remaining space partitions into 172.20.7.128/25 (128 IPs), 172.20.8.0/21 (2048 IPs), and 172.20.16.0/20 (4096 IPs). The largest block is 172.20.16.0/20.
Subnets must align on binary bit boundaries corresponding to their prefix lengths.
4
Calculate usable hosts for the largest unallocated block (172.20.16.0/20)
2^12 - 2 = 4096 - 2 = 4094 usable host IPv4 addresses.
Subtracting the network ID and broadcast address from total block addresses gives usable host count.

Key Concept

VLSM block allocation, binary boundary alignment, and unallocated subnet summarization
Estimated Time:3m 0s
Question 959Question →

A network technician is reviewing the physical and logical layout of a small branch office network that uses a 2-Tier (Collapsed Core) campus topology. Which two statements accurately describe key characteristics of this topology architecture? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: The core layer and distribution layer functions are combined into a single set of switches.; Access switches connect directly to the collapsed core/distribution devices.

Answer

The two correct traits of a 2-Tier (Collapsed Core) campus topology are that core and distribution layer functions are combined into unified switches, and access switches connect directly to these collapsed core/distribution devices.
In a 2-Tier (Collapsed Core) architecture, the traditional core and distribution layers are combined into a single switch tier, allowing access switches to connect directly to the collapsed core. This minimizes cost and maintenance while providing essential Layer 2/Layer 3 redundancy and connectivity.

Step-by-Step Solution

1
Identify the defining structural characteristic of a 2-Tier campus architecture.
The core layer and distribution layer are merged (collapsed) into a single functional layer.
This reduces hardware cost, management overhead, and cabling complexity for smaller networks.
2
Determine how access layer devices connect within this architecture.
Access switches uplink directly into the collapsed core switches.
Since there is no standalone distribution tier, the access switches connect straight to the combined core/distribution layer.

Key Concept

2-Tier (Collapsed Core) Network Topology Architecture
Question 960Question →

A Cisco Catalyst switch contains the following entry in its MAC address table for VLAN 10:

VLANMAC AddressTypePort
10000a.1111.2222DynamicGigabitEthernet0/1
10000b.3333.4444DynamicGigabitEthernet0/2

A network technician disconnects the host with MAC address 000a.1111.2222 from port GigabitEthernet0/1 and reconnects it to port GigabitEthernet0/3. The host immediately transmits an Ethernet frame destined for MAC address 000b.3333.4444 into port GigabitEthernet0/3 on VLAN 10. How will the switch handle MAC address learning and frame forwarding for this ingress traffic?

Show answer & explanation

Answer: It updates the MAC address table entry for 000a.1111.2222 to associate with GigabitEthernet0/3 and forwards the frame exclusively out GigabitEthernet0/2.

Answer

The switch updates the MAC address table entry for 000a.1111.2222 to point to GigabitEthernet0/3 and forwards the frame directly out GigabitEthernet0/2.
When an Ethernet frame arrives on port GigabitEthernet0/3, the switch reads the source MAC address 000a.1111.2222. Recognizing that this address was previously assigned to GigabitEthernet0/1, it performs a station move update by rewriting the MAC table entry to GigabitEthernet0/3. Next, the switch looks up the destination MAC address 000b.3333.4444. Since an entry already exists pointing to GigabitEthernet0/2, the switch forwards the frame as a known unicast transmission exclusively out GigabitEthernet0/2.

Step-by-Step Solution

1
Inspect the ingress frame's source MAC address and ingress port.
Source MAC 000a.1111.2222 is received on GigabitEthernet0/3.
Layer 2 switches perform MAC learning by examining the source MAC address of every incoming frame.
2
Update the MAC address table for station movement.
The dynamic entry for 000a.1111.2222 is updated from GigabitEthernet0/1 to GigabitEthernet0/3.
When a source MAC address is seen on a new interface, the switch updates the existing table mapping immediately.
3
Lookup the destination MAC address 000b.3333.4444 in the MAC address table.
Destination MAC 000b.3333.4444 is matched to egress port GigabitEthernet0/2.
Known unicast destination addresses result in point-to-point forwarding to the registered port.
4
Forward the Ethernet frame.
The frame is forwarded solely out GigabitEthernet0/2.
Because the destination port is known and distinct from the ingress port, no flooding or dropping occurs.

Key Concept

L2 Switching Station Movement and Known Unicast Forwarding
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