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Question 981Question →

A switch receives an Ethernet frame on port FastEthernet0/1. The source MAC address is 0000.1111.1111, and the unicast destination MAC address is 0000.2222.2222. The switch checks its MAC address table and finds no entry for 0000.2222.2222. What action does the switch take to handle this frame?

Show answer & explanation

Answer: Floods the frame out all operational interfaces except the ingress port FastEthernet0/1.

Answer

The switch floods the frame out all operational interfaces within the VLAN except the ingress port FastEthernet0/1.
When a Layer 2 switch receives a unicast frame whose destination MAC address is not currently in its MAC address table, it performs unknown unicast flooding. This forwards the frame out every active port belonging to the same VLAN, excluding the port on which the frame was received.

Step-by-Step Solution

1
Examine the source MAC address processing.
The switch records MAC address 0000.1111.1111 in its MAC address table mapped to port FastEthernet0/1 if it is not already present.
Switches learn MAC addresses dynamically from incoming frames' source MAC addresses.
2
Examine the destination MAC address lookup.
The destination MAC address 0000.2222.2222 is determined to be an unknown unicast address because it is not present in the MAC address table.
Forwarding decisions are made based on looking up the destination MAC address in the switch MAC address table.
3
Determine the forwarding behavior for unknown unicast traffic.
The switch floods the frame out all active switch ports in the VLAN, except for the incoming port FastEthernet0/1.
Flooding unknown unicast traffic ensures the destination host receives the packet regardless of which port it is connected to.

Key Concept

Unknown Unicast Flooding and MAC Address Table Lookup Operations
Question 982Question →

When a Layer 2 Ethernet switch receives an ingress frame, it processes the header information in a specific sequential order. Place the steps taken by the switch into the correct chronological order from first to last.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct order of switch operation is: 1) The frame arrives on an ingress port, 2) The switch learns or updates the source MAC address and port mapping in the MAC address table, 3) The switch performs a table lookup for the destination MAC address, and 4) The switch forwards or floods the frame out the appropriate port(s).
A Layer 2 Ethernet switch always follows a standard pipeline: frame reception on ingress, source MAC learning and table updating, destination MAC address lookup, and finally executing unicast forwarding or VLAN flooding.

Step-by-Step Solution

1
Receive ingress frame
The physical frame is received on an active Layer 2 switch port.
Initial reception triggers Layer 2 inspection.
2
Source MAC learning
The source MAC address is mapped to the ingress port in the MAC address table.
Switches always learn source MAC locations before executing forwarding logic.
3
Destination MAC lookup
The MAC address table is searched for the destination MAC address.
Determines whether the egress interface is known or unknown.
4
Frame forwarding decision
The frame is unicast forwarded to a single port or flooded across the VLAN (excluding ingress port).
Completes the Layer 2 delivery cycle.

Key Concept

Layer 2 Frame Ingress Processing and MAC Table Pipeline
Question 983Question →

An enterprise organization with 40 remote branch sites needs to connect all sites to a central data center. Direct communication between branch sites is rarely required, but predictable bandwidth to the central data center and minimal WAN circuit licensing costs are strict requirements. If a single branch WAN link fails, only that site should lose connectivity. Which WAN topology architecture best meets these operational and financial requirements?

Show answer & explanation

Answer: Hub-and-spoke topology

Answer

The hub-and-spoke topology best satisfies the requirements by concentrating connections at the central hub, minimizing total WAN circuit costs, and isolating individual branch link failures.
The hub-and-spoke topology connects each remote branch directly to a central hub (the data center). This provides independent connectivity per branch, requires only one WAN link per branch site, and minimizes overall cost while aligning perfectly with centralized traffic patterns.

Step-by-Step Solution

1
Analyze WAN traffic flow requirements
Traffic flow is primarily client-to-server (branch-to-central data center), with minimal branch-to-branch communication required.
Understanding traffic flows dictates whether direct site-to-site WAN circuits are necessary.
2
Evaluate cost and link scaling across candidate topologies
A hub-and-spoke design scales linearly with N−1N-1 links (39 links for 40 sites), whereas a full-mesh design requires 40×392=780\frac{40 \times 39}{2} = 780 links.
Minimizing WAN circuit licensing and circuit operational expenditure requires choosing a cost-efficient topology.
3
Verify fault domain isolation capabilities
In a hub-and-spoke architecture, each spoke operates on its own WAN connection to the hub, so a failure on one spoke circuit affects only that specific branch.
Ring and linear/daisy-chain topologies risk impacting multiple downstream sites upon a single link outage.

Key Concept

WAN Topology Architectures (Hub-and-Spoke vs Mesh vs Ring)
Estimated Time:2m 0s
Question 984Question →

A network engineer is configuring a Link Aggregation Control Protocol (LACP) EtherChannel between two switches. Which TWO channel-group mode combinations between the interconnected switch ports will successfully establish an operational EtherChannel bundle? (Select two.)

Select all that apply

Show answer & explanation

Answer: Active mode on the local switch port and active mode on the remote switch port; Active mode on the local switch port and passive mode on the remote switch port

Answer

The configurations that successfully form an LACP EtherChannel bundle are active-to-active and active-to-passive mode combinations.
For an IEEE 802.3ad Link Aggregation Control Protocol (LACP) EtherChannel to form, at least one interface must be set to active mode so that LACP frames are transmitted across the link. Consequently, combining an active interface with another active interface, or an active interface with a passive interface, results in a operational EtherChannel bundle.

Step-by-Step Solution

1
Analyze LACP mode behaviors
Active mode actively originates LACP negotiation frames. Passive mode only listens and responds to incoming LACP frames.
For negotiation to take place, at least one endpoint must generate negotiation frames.
2
Evaluate the mode combinations for compatibility
Active-to-active and active-to-passive form valid LACP EtherChannels. Passive-to-passive fails because neither interface transmits LACP negotiation frames. Active-to-desirable fails because LACP and PAgP are incompatible protocols.
EtherChannel negotiation protocols must match on both ends, and at least one port must actively send negotiation frames.

Key Concept

LACP EtherChannel Mode Negotiation Rules
Question 985Question →

A network administrator executes the global configuration command `vlan dot1q tag native` on a Cisco Catalyst switch. Interface GigabitEthernet1/0/1 on the switch is explicitly configured with `switchport mode trunk` and `switchport trunk native vlan 50`. Which TWO operational behaviors occur on this trunk interface as a result of this configuration? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: Egress frames originating from VLAN 50 exiting interface GigabitEthernet1/0/1 are encapsulated with an 802.1Q header specifying VLAN ID 50.; Ingress untagged Ethernet frames received on interface GigabitEthernet1/0/1 are dropped by the switch interface.

Answer

Enabling the global command `vlan dot1q tag native` forces the switch to place an 802.1Q tag on all native VLAN traffic (VLAN 50) egressing trunk ports and causes the switch to drop incoming untagged frames received on those trunk ports.
Under default 802.1Q operation, native VLAN traffic is sent untagged. Executing `vlan dot1q tag native` globally forces the switch to insert an 802.1Q tag into egress frames for the native VLAN (VLAN 50) and drop any untagged frames received on trunk interfaces.

Step-by-Step Solution

1
Analyze standard IEEE 802.1Q native VLAN default operation.
By default, IEEE 802.1Q trunks transmit traffic belonging to the configured native VLAN without adding a 4-byte 802.1Q header (untagged).
Backward compatibility with non-802.1Q legacy devices requires native VLAN traffic to remain untagged unless configured otherwise.
2
Determine the impact of the global command `vlan dot1q tag native` on egress traffic.
The command alters global switch behavior such that native VLAN frames (VLAN 50 in this scenario) are encapsulated with an 802.1Q header containing the native VLAN ID prior to egress transmission.
Tagging native VLAN traffic prevents VLAN hopping security attacks and ensures consistent identification across switch fabrics.
3
Determine the impact of the global command `vlan dot1q tag native` on ingress traffic.
Because the switch now expects tagged frames for all assigned VLANs on 802.1Q trunk links, any incoming untagged Ethernet frames arriving on the trunk interface are discarded.
Accepting untagged frames when native VLAN tagging is enabled would create ambiguity regarding frame classification.

Key Concept

Global 802.1Q Native VLAN Tagging Behavior
Estimated Time:2m 0s
Question 986Question →

An enterprise network architect is designing an IP addressing plan within the RFC 1918 private address space using the allocated 172.16.0.0/12172.16.0.0/12 block. The design requires server LAN subnets that can each support at least 1,0001,000 usable host IP addresses, as well as point-to-point infrastructure subnets requiring /30/30 prefixes. Which two statements regarding this subnetting design and IPv4 address allocation are correct?

Select all that apply

Show answer & explanation

Answer: A /22/22 subnet prefix provides 1,0221,022 usable host addresses, with 172.24.4.0/22172.24.4.0/22 spanning from network ID 172.24.4.0172.24.4.0 to broadcast address 172.24.7.255172.24.7.255.; The subnet 172.31.255.252/30172.31.255.252/30 represents the final valid /30/30 point-to-point subnet available within the assigned RFC 1918 172.16.0.0/12172.16.0.0/12 private block.

Answer

The two correct statements are the assertion that a /22 prefix provides 1,022 usable host addresses with 172.24.4.0/22 spanning up to broadcast address 172.24.7.255, and the assertion that 172.31.255.252/30 is the final valid /30 subnet within the RFC 1918 172.16.0.0/12 private block.
A /22 subnet provides 10 host bits, which allows for 1,022 usable hosts (2^10 - 2) and spans 172.24.4.0 through 172.24.7.255. Furthermore, 172.31.255.252/30 is the final /30 subnet within the 172.16.0.0/12 RFC 1918 private block, which terminates at 172.31.255.255.

Step-by-Step Solution

1
Calculate host capacity and range for a /22 subnet prefix
Host bits = 32 - 22 = 10 bits. Total IP addresses = 2^10 = 1,024. Usable host addresses = 2^10 - 2 = 1,022. The 3rd octet mask value is 252 (255.255.252.0), creating a 3rd octet block increment of 256 - 252 = 4. Therefore, subnet 172.24.4.0/22 spans from network ID 172.24.4.0 to broadcast address 172.24.7.255.
Determining the required prefix length for 1,000 hosts requires at least 10 host bits (1,022 usable), and validating the subnet boundaries ensures proper addressing without overlap.
2
Evaluate the RFC 1918 Class B private range boundaries
RFC 1918 defines Class B private space as 172.16.0.0/12, which ranges from 172.16.0.0 to 172.31.255.255.
Verifying private IPv4 address boundaries prevents using public addresses (such as 172.32.0.0/30) internally.
3
Verify the last /30 subnet within the RFC 1918 Class B block
A /30 subnet uses a mask of 255.255.255.252 with a block size of 4 in the fourth octet. The last block in the 172.31.255.0/24 subnet starts at 172.31.255.252 and ends at 172.31.255.255 (broadcast).
Confirming the upper boundary of 172.16.0.0/12 validates that 172.31.255.252/30 is the last valid /30 private subnet.

Key Concept

Subnetting host capacity formulas (2^n - 2) and RFC 1918 private IPv4 address range boundaries (172.16.0.0/12).
Question 987Question →

An enterprise organization is upgrading its campus network infrastructure to enable high-speed inter-VLAN routing between local client subnets directly within the wiring closet. The required device must perform wire-speed hardware packet forwarding between local VLANs using Switched Virtual Interfaces (SVIs) while continuing to provide Layer 2 access port connectivity for endpoints. Which network component should be deployed to meet these requirements?

Show answer & explanation

Answer: Layer 3 multilayer switch

Answer

Layer 3 multilayer switch
A Layer 3 multilayer switch performs both Layer 2 frame switching and Layer 3 IP routing. By configuring Switched Virtual Interfaces (SVIs), it routes traffic between VLANs at hardware wire-speed directly in the access layer, eliminating the need to pass traffic to an external router.

Step-by-Step Solution

1
Analyze the operational requirements specified in the scenario.
The target device must handle local Layer 2 endpoint connectivity while simultaneously routing IP packets between different local VLANs using SVIs.
Inter-VLAN routing requires a device operating at Layer 3 of the OSI model.
2
Evaluate candidate network components based on their functional roles.
A Layer 3 switch (multilayer switch) integrates Application-Specific Integrated Circuits (ASICs) for hardware-based packet routing between VLANs alongside standard Layer 2 bridging.
This offloads inter-VLAN routing from core edge routers and fulfills both Layer 2 access and Layer 3 routing requirements.

Key Concept

Multilayer (Layer 3) Switch Operational Roles and Inter-VLAN Forwarding
Estimated Time:1m 0s
Question 988Question →

A network administrator observes severe latency and frequent frame retries on an enterprise floor using a 2.4 GHz wireless deployment. Spectrum analysis reveals high co-channel interference (CCI) among neighboring access points. Which operational characteristic of the 2.4 GHz band primarily causes this channel reuse constraint when compared to the 5 GHz band?

Show answer & explanation

Answer: The 2.4 GHz spectrum offers only three non-overlapping 20 MHz channels in standard deployments, restricting spatial frequency reuse.

Answer

The 2.4 GHz spectrum offers only three non-overlapping 20 MHz channels in standard deployments, restricting spatial frequency reuse.
In 802.11 wireless networks using the 2.4 GHz ISM band, 20 MHz channels are spaced only 5 MHz apart. Consequently, only channels 1, 6, and 11 do not overlap with each other. In dense multi-AP deployments, having only three usable non-overlapping channels causes neighboring access points to operate on the same channel, generating high co-channel interference (CCI). In contrast, the 5 GHz band provides a much larger selection of non-overlapping channels, enabling far more flexible channel reuse.

Step-by-Step Solution

1
Analyze the channel spacing and bandwidth in the 2.4 GHz Wi-Fi spectrum.
The 2.4 GHz ISM band allocates channels spaced 5 MHz apart, while standard 802.11 channels require 20 MHz of channel width.
Understanding channel width requirements identifies how channels overlap.
2
Determine the maximum number of non-overlapping channels in 2.4 GHz.
Only 3 channels (channels 1, 6, and 11) can operate simultaneously in the same physical space without overlapping frequencies.
This strict limit creates spatial planning constraints for network designers.
3
Compare with 5 GHz channel availability to assess co-channel interference causes.
Because 5 GHz supports over 20 non-overlapping 20 MHz channels, 2.4 GHz environments suffer far more co-channel interference (CCI) in dense deployments.
The constraint of having only 3 non-overlapping channels directly leads to high CCI in multi-AP designs.

Key Concept

2.4 GHz vs 5 GHz Non-Overlapping Channels and Co-Channel Interference
Question 989Question →

An administrator is connecting switch SwitchA to switch SwitchB via interface GigabitEthernet1/0/15. Auto-MDIX has been manually disabled on interface GigabitEthernet1/0/15 using the `no mdix auto` command, and a standard Category 6 straight-through Ethernet cable is used between the two switches. The output of the `show interfaces GigabitEthernet1/0/15` command displays the following:

text
GigabitEthernet1/0/15 is down, line protocol is down
Hardware is Gigabit Ethernet, address is 0007.7d00.4a15
MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255

Which condition is the primary cause of the interface remaining in a down/down state?

Show answer & explanation

Answer: An incorrect cable pinout is used for connecting two like network switches when auto-MDIX is disabled.

Answer

The primary cause is an incorrect cable pinout used for connecting two like network switches when auto-MDIX is disabled.
Connecting two switches (like-to-like devices) requires a crossover cable so that the transmit pins on one end connect to the receive pins on the other end. While Auto-MDIX dynamically detects and corrects cable pinout mismatches, disabling Auto-MDIX with the `no mdix auto` command forces the switch interface to rely strictly on correct physical cable wiring. Using a straight-through cable between two switches with Auto-MDIX disabled prevents physical link detection, causing the interface status and line protocol to remain in a down/down state.

Step-by-Step Solution

1
Analyze the CLI output for interface status and line protocol state.
The output shows 'GigabitEthernet1/0/15 is down, line protocol is down', indicating a physical Layer 1 connectivity failure.
When both the interface and line protocol are down, the device cannot establish a physical electrical link with the remote peer.
2
Evaluate physical cable pinout requirements for like devices.
Switch-to-switch connections (like devices) transmit on pins 1,2 and receive on pins 3,6 (for 10/100/1000BASE-T). Connecting two like devices with a straight-through cable connects transmit pins to transmit pins and receive pins to receive pins.
Without Auto-MDIX automatically swapping transmit and receive pin pairs, a crossover cable is strictly required to establish physical link alignment.
3
Determine the impact of disabling Auto-MDIX.
Disabling Auto-MDIX (`no mdix auto`) forces the interface to rely entirely on correct physical cable pinouts, keeping the interface in a down/down state when connected via a straight-through cable.
Correcting the cable type to a crossover cable or re-enabling Auto-MDIX resolves the physical layer signaling failure.

Key Concept

Auto-MDIX and Cable Pinout Compatibility in Layer 1 Troubleshooting
Question 990Question →

An network administrator is setting up a traditional Cisco three-tier campus network. Which network tier is primarily responsible for directly attaching workstations, IP phones, and wireless access points while providing boundary security features such as port security?

Show answer & explanation

Answer: Access layer

Answer

The Access layer is responsible for direct endpoint connectivity and edge security control.
In a classic three-tier hierarchical campus network design, the Access layer switch provides direct physical and logical connectivity for end-user devices (workstations, printers, IP phones) and implements local port-level security features like Port Security and DHCP Snooping.

Step-by-Step Solution

1
Identify the primary functions required in the prompt
Directly connecting end-user endpoints (workstations, IP phones, APs) and applying edge security features such as port security.
Different network layers in Cisco hierarchical designs perform distinct operational tasks.
2
Map these functions to the correct Cisco three-tier layer
The Access layer provides end-node attachment and initial entry controls.
The Core layer focuses purely on high-speed switching, while the Distribution layer manages routing boundaries and aggregation.

Key Concept

Cisco 3-Tier Campus Architecture - Access Layer Role
Estimated Time:45s
Question 991Question →

A network administrator is converting an existing Layer 2 switch port channel into a routed Layer 3 EtherChannel interface on a Cisco switch. Which interface configuration command must be executed on both the physical member interfaces and the logical Port-channel interface to enable Layer 3 IP address assignment?

Show answer & explanation

Answer: no switchport

Answer

The 'no switchport' command must be configured on both the physical interfaces and the Port-channel interface.
To create a routed (Layer 3) EtherChannel on a Cisco Catalyst switch, the interface must be changed from Layer 2 mode to Layer 3 mode using the 'no switchport' command. This command must be executed on both the physical member interfaces and the logical Port-channel interface before an IP address can be configured.

Step-by-Step Solution

1
Identify the requirement for establishing a Layer 3 EtherChannel
Recognize that physical switch ports default to Layer 2 switchport operation.
By default, Cisco switch ports operate in Layer 2 mode and do not accept IP addressing commands.
2
Select the proper command to convert Layer 2 ports to Layer 3 ports
Apply 'no switchport' under the physical member interfaces and the Port-channel interface.
The 'no switchport' command turns off Layer 2 processing and makes the interface operate as a routed Layer 3 interface.

Key Concept

Layer 3 EtherChannel Configuration
Question 992Question →

A network engineer needs to implement an open standard, vendor-neutral Layer 2 neighbor discovery protocol across a mixed enterprise network containing both Cisco and non-Cisco devices. Which protocol defined under IEEE 802.1AB meets this requirement?

Show answer & explanation

Answer: Link Layer Discovery Protocol (LLDP)

Answer

Link Layer Discovery Protocol (LLDP) is the IEEE 802.1AB standard protocol used for Layer 2 discovery in multi-vendor network environments.
Link Layer Discovery Protocol (LLDP) is defined by IEEE 802.1AB. It provides vendor-neutral Layer 2 neighbor discovery functionality, making it ideal for heterogeneous network environments with devices from multiple vendors.

Step-by-Step Solution

1
Identify the protocol requirements from the scenario.
The scenario specifies an open-standard, vendor-neutral Layer 2 discovery protocol governed by IEEE 802.1AB.
Multivendor environments cannot rely on proprietary protocols like CDP across non-Cisco switches.
2
Evaluate candidate protocols against IEEE standards.
LLDP is explicitly defined under the IEEE 802.1AB standard for network device discovery.
LLDP allows heterogeneous network devices to advertise capabilities, management IP, and interface details across vendor boundaries.

Key Concept

Layer 2 Discovery Protocols: CDP vs. LLDP Standards
Question 993Question →

A network administrator executes the command `show etherchannel summary` on a Cisco switch to troubleshoot a newly configured EtherChannel link. The output displays the following information:

text Flags: D - down P - bundled in port-channel I - stand-alone s - suspended H - Hot-standby (LACP only) S - Layer2 U - in use Group Port-channel Protocol Ports ------+--------------+---------+----------------------------------------------- 1 Po1(SU) LACP Gi0/1(I) Gi0/2(I)

Based on the output, which configuration state is the primary cause of both physical member interfaces remaining in the `(I)` stand-alone state?

Show answer & explanation

Answer: Both interconnecting switches have their physical member interfaces configured in LACP passive mode.

Answer

Both interconnecting switches have their physical member interfaces configured in LACP passive mode.
In LACP negotiation, an interface configured in passive mode will listen for LACP packets but will never initiate transmission of LACP PDUs. If both switches across a link are set to passive mode, neither switch sends LACP packets. Consequently, LACP negotiation never completes, and member interfaces remain in the stand-alone state indicated by the flag (I) in the show etherchannel summary output.

Step-by-Step Solution

1
Analyze the output of the show etherchannel summary command
Port-channel status is SU (Layer 2, in use), protocol is LACP, but member ports GigabitEthernet0/1 and GigabitEthernet0/2 are marked with flag (I).
According to the output flags, (I) indicates stand-alone mode, meaning the physical interfaces are operating independently and have not successfully negotiated into the bundled channel group.
2
Evaluate LACP mode negotiation mechanics
LACP supports two modes: active (initiates negotiation by sending LACP PDUs) and passive (responds to LACP PDUs but does not initiate them).
At least one side of the link must be set to active mode to initiate the exchange of LACP packets.
3
Identify the cause of stand-alone state
When both sides are configured as passive, neither switch initiates LACP PDU exchange. As a result, LACP negotiation fails to start, leaving member ports in the stand-alone (I) state.
Matching passive-passive modes fail to negotiate an operational EtherChannel.

Key Concept

LACP Mode Negotiation and Verification Flags
Question 994Question →

A network administrator is migrating a pair of trunk links connecting two distribution switches to a routed Layer 3 EtherChannel using IEEE 802.3ad LACP. Interfaces GigabitEthernet1/0/1 and GigabitEthernet1/0/2 need to be bundled into Port-channel 5 with IPv4 address 10.0.5.1/3010.0.5.1/30 assigned to the logical interface. In what operational sequence must these CLI configuration steps be executed on the switch to successfully create this Layer 3 EtherChannel?

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct operational sequence begins by selecting physical member interfaces via interface range mode, converting them to Layer 3 routed ports using `no switchport`, binding them to LACP bundle 5 with `channel-group 5 mode active`, entering `interface Port-channel 5` configuration mode, and finally assigning IPv4 address 10.0.5.1/3010.0.5.1/30 directly to the logical port-channel.
To build an operational Layer 3 LACP EtherChannel, physical member links must first be selected and converted into routed interfaces (`no switchport`). Adding these converted interfaces to a channel group with `mode active` automatically creates a Layer 3 logical port-channel and starts LACP negotiation. Finally, configuration transitions to `interface Port-channel 5`, where the IP address is applied to the logical bundle.

Step-by-Step Solution

1
Execute `interface range GigabitEthernet1/0/1 - 2`.
Enters range interface configuration mode for both physical member interfaces.
Configuration commands must be applied simultaneously to member interfaces to maintain identical operational states.
2
Execute `no switchport` on the physical interface range.
Converts physical member interfaces from Layer 2 switchports into Layer 3 routed ports.
Member interfaces must be routed ports prior to group assignment so that Cisco IOS instantiates a Layer 3 Port-channel interface.
3
Execute `channel-group 5 mode active`.
Instantiates Port-channel 5 and enables active IEEE 802.3ad LACP negotiation on the physical interfaces.
Active mode ensures the switch actively sends LACP Link Aggregation Control Protocol Data Units (LACPDUs) to negotiate EtherChannel formation.
4
Execute `interface Port-channel 5`.
Enters interface configuration sub-mode for logical interface Port-channel 5.
Layer 3 protocol configuration and IP routing parameters belong to the logical bundle interface.
5
Execute `ip address 10.0.5.1 255.255.255.252` on the port-channel interface.
Configures the IP address and subnet mask on the logical EtherChannel bundle.
In Layer 3 EtherChannels, packets are routed to the port-channel interface, which then distributes traffic across physical member links using the load-balancing hash.

Key Concept

Layer 3 EtherChannel LACP Configuration Sequence
Question 995Question →

Match each IPv6 address category on the left with its designated reserved prefix block on the right according to RFC standards.

Click a left item, then click its matching right item

Items

Global Unicast
Unique Local
Link-Local
Multicast

Matches

Show answer & explanation

Answer

Global Unicast corresponds to 2000::/3, Unique Local corresponds to fc00::/7, Link-Local corresponds to fe80::/10, and Multicast corresponds to ff00::/8.
Each IPv6 category matches its standards-based prefix block: Global Unicast matches 2000::/3, Unique Local matches fc00::/7, Link-Local matches fe80::/10, and Multicast matches ff00::/8.

Step-by-Step Solution

1
Identify the Global Unicast prefix allocation.
Global Unicast uses binary prefix 001, which maps to 2000::/32000::/3.
RFC 4291 reserves 2000::/32000::/3 for publicly routable global unicast addresses.
2
Identify the Unique Local address range.
Unique Local uses binary prefix 1111 110, which maps to fc00::/7fc00::/7.
RFC 4193 reserves fc00::/7fc00::/7 for private enterprise network addressing.
3
Identify the Link-Local address prefix.
Link-Local uses binary prefix 1111 1110 10, which maps to fe80::/10fe80::/10.
RFC 4291 defines fe80::/10fe80::/10 for communications confined to a local physical or virtual link.
4
Identify the Multicast address range.
Multicast uses binary prefix 1111 1111, which maps to ff00::/8ff00::/8.
RFC 4291 assigns all IPv6 addresses starting with FF to multicast functionality.

Key Concept

IPv6 Address Scopes and Prefix Allocations
Question 996Question →

A network administrator is assigning IPv4 addresses to host interfaces within the 10.50.12.0/2610.50.12.0/26 subnet. Which of the following IPv4 addresses are valid usable host addresses on this subnet?

Select all that apply

Show answer & explanation

Answer: 10.50.12.110.50.12.1; 10.50.12.5010.50.12.50

Answer

The addresses 10.50.12.110.50.12.1 and 10.50.12.5010.50.12.50 are valid usable host addresses on the 10.50.12.0/2610.50.12.0/26 subnet.
For a /26/26 prefix, 6 host bits yield 64 total IP addresses. With a network address of 10.50.12.010.50.12.0, the subnet broadcast address is 10.50.12.6310.50.12.63. The valid usable host range spans from 10.50.12.110.50.12.1 to 10.50.12.6210.50.12.62. Therefore, 10.50.12.110.50.12.1 and 10.50.12.5010.50.12.50 are valid host addresses.

Step-by-Step Solution

1
Determine the subnet size from the CIDR prefix.
A /26/26 prefix leaves 32−26=632 - 26 = 6 host bits. The total block size is 26=642^6 = 64 addresses.
Host bits determine the size of the IP block for a given prefix.
2
Identify the network address and broadcast address for the subnet.
The network address is 10.50.12.010.50.12.0. The broadcast address is 10.50.12.6310.50.12.63 (0+64−10 + 64 - 1).
The first address in a block is reserved for the network ID, and the last address is reserved for the broadcast ID.
3
Calculate the usable host address range.
The usable host address range is 10.50.12.110.50.12.1 through 10.50.12.6210.50.12.62.
Usable host addresses exclude both the network ID and the broadcast ID (2n−22^n - 2).
4
Evaluate the given choices against the usable host range.
10.50.12.110.50.12.1 and 10.50.12.5010.50.12.50 fall within the [10.50.12.1,10.50.12.62][10.50.12.1, 10.50.12.62] range, while 10.50.12.010.50.12.0 is the network ID and 10.50.12.6310.50.12.63 is the broadcast ID.
Only addresses inside the calculated usable host range can be assigned to host interfaces.

Key Concept

Subnet Host Range Calculation
Estimated Time:45s
Question 997Question →

A network administrator is troubleshooting an addressing issue on a branch office switch. A host computer on VLAN 10 has been manually configured with the IP address 172.25.107.191172.25.107.191 and subnet mask 255.255.255.192255.255.255.192. The switch SVI interface serving as the default gateway for VLAN 10 is assigned 172.25.107.129/26172.25.107.129/26. The host is unable to ping its default gateway or communicate beyond its local segment. Which statement correctly identifies the cause of this connectivity failure?

Show answer & explanation

Answer: The assigned address 172.25.107.191172.25.107.191 is the broadcast address for the subnet and cannot be utilized as a valid host IP address.

Answer

The host address 172.25.107.191 is the broadcast address for the 172.25.107.128/26 subnet and is invalid for host assignment.
The correct answer accurately identifies that 172.25.107.191 is the directed broadcast address for the 172.25.107.128/26 network segment. For a /26 prefix, the block size is 64, giving a network ID of 172.25.107.128 and a broadcast ID of 172.25.107.191. Because broadcast addresses cannot be configured as valid unicast endpoints, the host network stack fails to process traffic correctly.

Step-by-Step Solution

1
Determine the subnet mask prefix length and block size.
A subnet mask of 255.255.255.192255.255.255.192 corresponds to CIDR notation /26/26. The block size in the fourth octet is calculated as 256−192=64256 - 192 = 64.
Calculating the block size identifies subnet boundaries.
2
Calculate the subnet boundaries for the gateway IP 172.25.107.129172.25.107.129.
Subnet multiples of 64 in the 4th octet are 0, 64, 128, and 192. The gateway IP 172.25.107.129172.25.107.129 falls into the network 172.25.107.128/26172.25.107.128/26.
Identifying the network ID establishes the IP range for VLAN 10.
3
Calculate the network address, usable host range, and broadcast address.
Network Address: 172.25.107.128172.25.107.128. First Usable Host: 172.25.107.129172.25.107.129. Last Usable Host: 172.25.107.190172.25.107.190. Broadcast Address: 172.25.107.191172.25.107.191.
Formula 2n−22^n - 2 yields 62 usable host IPs (26−2=622^6 - 2 = 62).
4
Evaluate the validity of the host's manually assigned IP address 172.25.107.191172.25.107.191.
The address 172.25.107.191172.25.107.191 matches the subnet broadcast address exactly.
Broadcast addresses are reserved for network-wide broadcasts and cannot be bound to network adapters as valid unicast host IPs.

Key Concept

Subnet Broadcast Address Identification and Usable Host Range Calculation
Question 998Question →

A network technician is troubleshooting interface and cabling symptoms across enterprise switches. Match each Cisco IOS interface status output or error counter on the left with its most probable root cause on the right.

Click a left item, then click its matching right item

Items

Interface output displays 'GigabitEthernet0/1 is down, line protocol is down'.
Interface output displays 'FastEthernet0/2 is up, line protocol is down'.
Interface statistics show an increasing counter of Late Collisions.
Interface statistics show high CRC and Input Errors without collisions.

Matches

Show answer & explanation

Answer

Match 'down/down' to Layer 1 physical failure; 'up/down' to Layer 2 data link issue; 'Late Collisions' to duplex mismatch; and 'CRC errors' to physical media impairment or electromagnetic interference.
Each status combination and error counter directly corresponds to its underlying network layer or physical cabling cause. An interface status of 'down/down' reflects Layer 1 physical disconnection. An interface status of 'up/down' indicates Layer 2 data link failure. Late collisions indicate a duplex configuration mismatch. CRC errors without collisions indicate physical frame corruption due to cable degradation or electrical interference.

Step-by-Step Solution

1
Analyze interface operational states.
Identify that 'down/down' indicates a Physical Layer (Layer 1) connectivity issue, while 'up/down' signifies operational Layer 1 but failed Data Link Layer (Layer 2) keepalives or framing.
Cisco IOS interface output separates physical signaling (interface state) from data link communication (line protocol state).
2
Differentiate between specific interface error counters.
Link Late Collisions to duplex mismatches where collision detection window boundaries are violated, and associate CRC errors with frame corruption due to faulty cabling or interference.
Accurate error counter diagnosis isolates misconfigurations from physical cabling damage.

Key Concept

Cisco IOS Interface Status and Troubleshooting Error Counters
Question 999Question →

Which two modifications are performed on a 48-bit MAC address when generating a 64-bit IPv6 interface identifier using the EUI-64 process? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: The 16-bit hexadecimal value FFFE is inserted into the middle of the MAC address.; The 7th bit (Universal/Local bit) of the first byte of the MAC address is inverted.

Answer

Generating an IPv6 EUI-64 interface identifier requires inserting the 16-bit hexadecimal value FFFE into the middle of the 48-bit MAC address and inverting the 7th bit (Universal/Local bit) of the first byte.
The standard EUI-64 process creates a 64-bit interface ID from a 48-bit MAC address by inserting the 16-bit hexadecimal value FFFE between the OUI and vendor-assigned portion, and inverting the 7th bit (Universal/Local bit) of the first byte.

Step-by-Step Solution

1
Split the 48-bit MAC address into two 24-bit halves.
The Organizationally Unique Identifier (OUI) forms the upper 24 bits and the NIC extension forms the lower 24 bits.
EUI-64 requires extending the address length at its midpoint.
2
Insert FFFE between the two 24-bit halves.
The address expands from 48 bits to 64 bits.
FFFE acts as the designated padding delimiter specified by IEEE and IPv6 standards.
3
Invert the 7th bit (Universal/Local bit) of the first byte.
If the 7th bit was 0 (indicating a burned-in MAC address), it becomes 1 in the IPv6 interface identifier.
IPv6 standardizes global uniqueness by setting the U/L bit to 1 for universally unique interface IDs.

Key Concept

EUI-64 Interface Identifier Derivation
Question 1000Question →

A network technician is connecting legacy network devices in a lab environment where Auto-MDIX is explicitly disabled on all switch interfaces. Which two statements correctly describe the cable pinout requirements and cabling types for these connections? (Choose two.)

Select all that apply

Show answer & explanation

Answer: Connecting two network switches directly via FastEthernet interfaces requires a crossover cable when Auto-MDIX is disabled.; An Ethernet crossover cable connects transmit pins 1 and 2 on one RJ-45 connector to receive pins 3 and 6 on the opposite connector.

Answer

Connecting two network switches directly via FastEthernet interfaces requires a crossover cable when Auto-MDIX is disabled, and an Ethernet crossover cable connects transmit pins 1 and 2 on one RJ-45 connector to receive pins 3 and 6 on the opposite connector.
When connecting identical network device types (such as switch-to-switch or router-to-router) without Auto-MDIX feature active, a crossover cable must be used so that the transmit pins (1 and 2) on one end link to the receive pins (3 and 6) on the opposite end.

Step-by-Step Solution

1
Identify the device types being connected
Connecting a switch to a switch involves two like devices (MDI-X to MDI-X).
Like devices transmit and receive on identical pin pairs.
2
Determine the required cable type without Auto-MDIX
A crossover cable is required for switch-to-switch connections.
Without Auto-MDIX to automatically swap transmit and receive signals, the physical cable must perform the crossover function.
3
Verify the pinout wiring for FastEthernet crossover cables
Pins 1 and 2 on one connector connect to pins 3 and 6 on the opposite connector.
FastEthernet (100BASE-TX) uses pairs 1/2 and 3/6 for transmit (Tx) and receive (Rx).

Key Concept

Ethernet Cable Pinouts and MDI/MDI-X Device Interfaces
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