All practice questions

1987 questions

All types1,987 Multiple choice1,020 Multiple select452 Numeric18 Matching229 Ordering203 Fill in the blank22 Short answer43

Question 961Question →

A network administrator executes the following command on switch SW-1 to troubleshoot connectivity to an adjacent network device:

text
SW-1# show lldp neighbors detail
------------------------------------------------
Local Intf: Gi0/1
Chassis id: 0014.f25a.a100
Port id: GigabitEthernet1/0/24
Port Description: Trunk Link to SW-1
System Name: SW-2
System Description: Cisco IOS Software, C3750E Software (C3750E-UNIVERSALK9-M)
Time remaining: 98 seconds
System Capabilities: B, R
Enabled Capabilities: B
Management Addresses:
IP: 10.1.10.2
Auto Negotiation - supported, enabled
Physical media capabilities:
1000baseT(FD)
Media Attachment Unit type: 30
VLAN ID: 20

Based on the output provided, which conclusion accurately describes the neighbor relationship and port configuration?

The adjacent switch SW-2 is connected via its interface GigabitEthernet1/0/24 to SW-1's local interface GigabitEthernet0/1, operating with a port VLAN ID of 20 and management address 10.1.10.2.

SW-1 is physically connected using its local port GigabitEthernet1/0/24 to SW-2's remote port GigabitEthernet0/1.

A native VLAN mismatch is present because LLDP cannot report VLAN ID 20 on interface GigabitEthernet0/1 unless VLAN 1 is configured as the untagged native VLAN.

The neighbor device SW-2 is operating as a Layer 3 router because 'Enabled Capabilities: B' indicates routing functions are active on interface GigabitEthernet1/0/24.

Show answer & explanation

Answer: The adjacent switch SW-2 is connected via its interface GigabitEthernet1/0/24 to SW-1's local interface GigabitEthernet0/1, operating with a port VLAN ID of 20 and management address 10.1.10.2.

Answer

The adjacent switch SW-2 is connected via its interface GigabitEthernet1/0/24 to SW-1's local interface GigabitEthernet0/1, operating with a port VLAN ID of 20 and management address 10.1.10.2.

The output of 'show lldp neighbors detail' shows that local interface Gi0/1 on SW-1 is connected to remote port GigabitEthernet1/0/24 on system SW-2. It also displays SW-2's management IP (10.1.10.2), system capabilities, and the advertised Port VLAN ID of 20.

Step-by-Step Solution

Identify local vs. remote interface designations in the LLDP CLI output.

'Local Intf: Gi0/1' is the local interface on SW-1. 'Port id: GigabitEthernet1/0/24' represents the interface on the remote neighbor (SW-2).

Layer 2 discovery outputs distinguish between local ports where traffic is received and remote port IDs advertised by neighbors.

Analyze System Name, System Capabilities, and Management Addresses.

System Name is SW-2, Management IP is 10.1.10.2, and Enabled Capabilities is 'B' (Bridge/Switch).

Capability code 'B' stands for Bridge/Switch, proving the active role of the device is Layer 2 switching.

Evaluate the IEEE 802.1 TLV Port VLAN ID information.

'VLAN ID: 20' reflects the advertised Port VLAN ID (PVID) associated with the link.

LLDP advertises PVID through Organizationally Specific TLVs, allowing operators to verify VLAN settings on connected links.

Key Concept

Interpretation of IEEE 802.1AB LLDP detailed neighbor table outputs and TLV fields.

Estimated Time:2m 0s

Question 962Question →

A network administrator is attempting to establish an operational Layer 3 EtherChannel using LACP between two Cisco switches. After applying the initial configuration, the administrator issues the `show etherchannel summary` command on Switch1 and observes the following output:

Flags: D - down P - bundled in port-channel
I - stand-alone s - suspended
H - Hot-standby s - Layer2
R - Layer3 U - in use

Group Port-channel Protocol Ports
------+-------------+-----------+-----------------------------------------------
1 Po1(SD) LACP Gi0/1(D) Gi0/2(D)

Which configuration change on Switch1 is required to allow Port-Channel 1 to operate successfully as a Layer 3 EtherChannel?

Configure the `no switchport` command on physical member interfaces GigabitEthernet0/1 and GigabitEthernet0/2 before adding them to the channel group.

Change the LACP mode on physical member interfaces GigabitEthernet0/1 and GigabitEthernet0/2 from `active` to `desirable`.

Configure the channel group mode to `passive` on both switches to initialize LACP negotiation.

Set matching native VLANs on GigabitEthernet0/1 and GigabitEthernet0/2 to enable Layer 3 packet transmission.

Show answer & explanation

Answer: Configure the `no switchport` command on physical member interfaces GigabitEthernet0/1 and GigabitEthernet0/2 before adding them to the channel group.

Answer

Configure the `no switchport` command on physical member interfaces GigabitEthernet0/1 and GigabitEthernet0/2 before adding them to the channel group.

For a Layer 3 EtherChannel to operate correctly, physical member interfaces must be explicitly configured as routed ports using the `no switchport` command. The flag `S` in `Po1(SD)` indicates the interface bundle is operating at Layer 2. Converting the physical member ports to Layer 3 allows the EtherChannel to transition to the `RU` (Layer 3, in use) operational state.

Step-by-Step Solution

Analyze the output flags from `show etherchannel summary`.

The logical interface displays `Po1(SD)`, where `S` indicates Layer 2 operational mode and `D` indicates the channel is Down. Member interfaces display `(D)` for down.

The flag `S` indicates the physical interfaces are currently operating as Layer 2 switchports rather than Layer 3 routed ports.

Identify the requirement for creating a Layer 3 EtherChannel in Cisco IOS.

Both the physical member interfaces and the logical port-channel interface must be configured with `no switchport` to function as routed interfaces.

If physical interfaces remain in Layer 2 switchport mode, the port-channel cannot bundle them into a Layer 3 (`R`) operational state.

Determine the corrective CLI commands.

Navigate to `interface range GigabitEthernet0/1 - 2` and execute `no switchport`, then re-assign `channel-group 1 mode active`.

Disabling switchport mode allows the interfaces to negotiate as Layer 3 routed ports and transition the port-channel state flag from `SD` to `RU` (Layer 3, in use).

Key Concept

Layer 3 EtherChannel Member Configuration

Estimated Time:1m 30s

Question 963Question →

A remote branch office requires a dedicated network device to route traffic between local department subnets, isolate broadcast domains, and establish an encrypted site-to-site IPsec tunnel to the main corporate data center. Which network component is designed to perform these combined operational functions?

An enterprise router

An unsegmented Layer 2 switch

A hosted Type 2 hypervisor

A Lightweight Access Point in Local mode

Show answer & explanation

Answer: An enterprise router

Answer

An enterprise router is designed to route traffic across distinct IP subnets, separate broadcast domains, and terminate site-to-site IPsec VPN connections.

The option specifying an enterprise router correctly identifies the device operating at Layer 3 capable of making forwarding decisions based on IP addresses, isolating broadcast domains on each interface, and providing WAN capabilities such as site-to-site IPsec VPN encryption.

Step-by-Step Solution

Analyze the operational requirements stated in the scenario.

The device must perform inter-VLAN IP routing, separate broadcast domains, and terminate site-to-site IPsec VPN tunnels.

Identifying the required OSI layer operations (Layer 3 IP routing and security encapsulation) narrows down the appropriate hardware component.

Evaluate candidate network components against these requirements.

Routers operate at Layer 3, separating broadcast domains at each interface and routing IP packets while supporting WAN services like VPNs.

Layer 2 switches operate within a single broadcast domain per VLAN, Type 2 hypervisors manage VMs on top of an OS, and Local mode LAPs encapsulate wireless frames for a centralized WLC.

Key Concept

Network Component Roles (Routers vs Switches vs Access Points vs Hypervisors)

Estimated Time:1m 0s

Question 964Question →

In a standard two-tier Spine-Leaf data center architecture, to which switches does every leaf switch directly connect?

To every spine switch in the network fabric

To adjacent leaf switches to break up broadcast domains

To host servers running Type 1 hypervisors to handle inter-spine forwarding

To inter-switch trunks configured with STP PortFast across all leaf nodes

Show answer & explanation

Answer: To every spine switch in the network fabric

Answer

Every leaf switch connects directly to every spine switch in the network fabric.

In a Spine-Leaf (Clos) architecture, every leaf switch connects to every spine switch in a full mesh layout between tiers. Leaf switches do not connect to each other, nor do spine switches connect to each other. This design provides consistent latency and maximum redundancy.

Step-by-Step Solution

Identify the structural rule of a two-tier Spine-Leaf (Clos) data center topology.

In a two-tier Spine-Leaf architecture, every leaf switch must connect to every spine switch in the fabric.

This guarantees equal path distance (predictable latency) and maximum bandwidth between any two leaf switches.

Verify inter-switch connection rules within the leaf and spine layers.

Leaf switches do not connect directly to other leaf switches, and spine switches do not connect directly to other spine switches.

Maintaining strict bipartite connectivity ensures efficient Equal-Cost Multi-Path (ECMP) routing across all available paths.

Key Concept

Spine-Leaf Architecture Bipartite Connectivity

Estimated Time:45s

Question 965Question →

A network administrator executes the `show interfaces GigabitEthernet0/2` command on a Cisco IOS switch to investigate frame loss on a point-to-point connection. The command output displays the following status:

text
GigabitEthernet0/2 is up, line protocol is up
Full-duplex, 1000Mb/s, media type is 10/100/1000BaseTX
14205 input errors, 14205 CRC, 0 frame, 0 overrun, 0 ignored
0 output errors, 0 collisions, 0 interface resets

Based on the CLI output, which condition is the most likely cause of the observed interface statistics?

Damaged copper cabling or high levels of electromagnetic interference along the cable path

An incorrect Ethernet pinout selection between legacy network devices with Auto-MDIX disabled

A native VLAN configuration mismatch between trunk interfaces at opposite ends of the link

A misinterpretation of incoming CDP or LLDP discovery protocol Type-Length-Value fields

Show answer & explanation

Answer: Damaged copper cabling or high levels of electromagnetic interference along the cable path

Answer

Damaged copper cabling or high levels of electromagnetic interference along the cable path is the most likely cause of the CRC errors.

CRC errors occur when the receiving switch interface calculates a Frame Check Sequence (FCS) that does not match the FCS attached to the incoming frame. On a link with zero collisions and correctly operating full-duplex negotiation, high CRC error counts are almost exclusively caused by physical layer media degradation, such as a damaged twisted-pair cable, loose RJ-45 connectors, bad patch panel terminations, or electromagnetic interference (EMI).

Step-by-Step Solution

Analyze the interface status and duplex settings in the CLI output.

The interface status is 'up/up' and operating in Full-duplex at 1000Mb/s.

Verifies that Layer 1 physical link and Layer 2 line protocol are active, ruling out complete link loss caused by cabling mismatch.

Examine the error counters in the interface statistics.

Input errors equal 14,205, with all 14,205 registered specifically as CRC errors, while collisions remain 0.

A CRC error occurs when a frame's calculated Frame Check Sequence (FCS) does not match the checksum value sent by the transmitting node.

Correlate CRC errors with potential root causes.

Since duplex is matched and no collisions exist, frame corruption during transit points directly to physical Layer 1 media degradation (faulty cables, bad punch-downs, or external EMI noise).

Late collisions would indicate a duplex mismatch, whereas CRC errors with zero collisions indicate corruption of bits while crossing the physical medium.

Key Concept

Interface CRC and Input Errors Troubleshooting

Question 966Question →

An administrator is troubleshooting a connectivity issue on interface GigabitEthernet1/0/5, which connects to an IP phone with a co-located workstation. The IP phone successfully registers with the Voice over IP (VoIP) server, but the workstation connected to the phone cannot communicate on the network.

The output of `show interfaces status` displays:
text
Port Name Status Vlan Duplex Speed Type
Gi1/0/5 Workstation_PC connected inactive a-full a-1000 10/100/1000BaseTX

Additionally, `show running-config interface GigabitEthernet1/0/5` yields:
text
interface GigabitEthernet1/0/5
switchport mode access
switchport access vlan 30
switchport voice vlan 200

Which condition explains why the VLAN status displays as `inactive`, and what configuration step is required to restore workstation connectivity?

Access VLAN 30 does not exist in the switch VLAN database; configuring `vlan 30` in global configuration mode will activate the access VLAN and restore traffic forwarding for the workstation.

The port experiences an 802.1Q native VLAN mismatch because VLAN 30 is not designated as native; issuing `switchport trunk native vlan 30` under interface mode will allow untagged frames to pass.

The access port disabled frame forwarding because PortFast is omitted; entering `spanning-tree portfast` on interface GigabitEthernet1/0/5 is required to bridge the data and voice broadcast domains.

The port was placed into an err-disabled state due to a security violation; executing `shutdown` followed by `no shutdown` on interface GigabitEthernet1/0/5 will clear the port state.

Show answer & explanation

Answer: Access VLAN 30 does not exist in the switch VLAN database; configuring `vlan 30` in global configuration mode will activate the access VLAN and restore traffic forwarding for the workstation.

Answer

Access VLAN 30 does not exist in the switch VLAN database; configuring `vlan 30` in global configuration mode will activate the access VLAN and restore traffic forwarding for the workstation.

In Cisco IOS, when an interface is assigned to an access VLAN that is not currently present in the switch's VLAN database, the operational status of that VLAN on the port is set to `inactive`. As a result, untagged traffic from the attached workstation is dropped. The voice VLAN continues to operate independently because VLAN 200 exists in the database. Creating VLAN 30 using `vlan 30` in global configuration mode adds it to the VLAN database and immediately restores the port's access VLAN to active status.

Step-by-Step Solution

Analyze the CLI output from `show interfaces status` and `show running-config interface GigabitEthernet1/0/5`.

The interface status is `connected`, but the assigned VLAN column shows `inactive`. The interface configuration shows `switchport access vlan 30` and `switchport voice vlan 200`.

An `inactive` VLAN status in `show interfaces status` occurs specifically when a port is assigned to a VLAN ID that does not exist in the switch's VLAN database (`vlan.dat`).

Determine why the IP phone functions while the workstation fails.

Voice VLAN 200 exists in the VLAN database and is active, allowing tagged voice frames from the phone to forward. VLAN 30 is missing from the VLAN database, causing untagged data frames from the workstation to be dropped.

Cisco IOS handles voice and access traffic separately on multi-VLAN access ports; missing access VLAN definitions render only the data VLAN inactive.

Identify the required remediation command sequence.

Enter global configuration mode and create VLAN 30 using the command `vlan 30`.

Creating the VLAN in the VLAN database immediately changes the port's operational access VLAN status from `inactive` to active without modifying interface commands.

Key Concept

VLAN Database Existence and Access Port Operational States

Estimated Time:2m 0s

Question 967Question →

A network administrator is selecting a transport layer protocol for a real-time voice streaming service where low transmission latency is required and dropped packets should not be retransmitted. Which characteristic of User Datagram Protocol (UDP) makes it better suited than Transmission Control Protocol (TCP) for this application?

UDP operates with a lightweight fixed 8-byte header and no connection setup overhead.

UDP ensures zero packet loss by utilizing dynamic windowing and automatic sequence number tracking.

UDP incorporates a variable 20-to-60 byte header to dynamically alter transmission rates based on network congestion.

UDP establishes low-latency virtual circuits prior to data transfer by performing a abbreviated two-way handshake.

Show answer & explanation

Answer: UDP operates with a lightweight fixed 8-byte header and no connection setup overhead.

Answer

UDP operates with a lightweight fixed 8-byte header and no connection setup overhead.

The choice highlighting UDP's lightweight fixed 8-byte header and lack of connection setup overhead is correct because UDP is a stateless, connectionless protocol designed for low-latency delivery where packet retransmission is undesirable.

Step-by-Step Solution

Analyze application requirements

Real-time voice traffic requires minimal delay and does not benefit from retransmitting delayed packets.

Retransmitted voice packets arrive too late to be useful in a live conversation.

Evaluate transport layer protocols

UDP is connectionless and has a minimal 8-byte header size compared to TCP's 20-byte minimum header and mandatory 3-way handshake.

UDP avoids the latency overhead associated with session establishment, sequencing, and flow control.

Key Concept

UDP vs TCP Header and Connection Mechanics

Estimated Time:45s

Question 968Question →

Match each network application operational requirement or protocol scenario on the left with its corresponding transport layer protocol implementation characteristic on the right.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Real-time VoIP pairs with UDP 8-byte low-latency transport; BGP peering pairs with TCP port 179 stateful reliable transport; TFTP image download pairs with UDP port 69 and application-layer ACKs; SNMP polling pairs with UDP port 161 stateless request-response.

Real-time VoIP demands UDP for minimal latency and an 8-byte header; BGP requires TCP on port 179 for reliable ordered routing updates; TFTP uses UDP port 69 and handles reliability at the application layer; SNMP polling uses UDP port 161 for lightweight stateless data collection.

Step-by-Step Solution

Analyze transport latency and retransmission requirements for voice traffic

Real-time VoIP requires low latency and predictable delivery without retransmitting dropped packets, matching UDP's 8-byte header fixed structure.

Retransmitted voice packets arrive too late to be decoded into meaningful audio.

Analyze reliability requirements for control plane routing protocols

BGP demands strict sequence ordering and guaranteed arrival of routing table updates, matching TCP port 179 stateful behavior.

BGP does not implement its own transport retransmission mechanism.

Evaluate bootloader file transfer architecture

TFTP uses UDP port 69 while handling stop-and-wait acknowledgments at the application layer.

Simple boot ROMs require minimal transport stack overhead while still needing basic delivery validation.

Evaluate high-frequency network monitoring polling overhead

SNMP polling uses UDP port 161 for stateless queries to prevent memory exhaustion on monitoring hosts.

Establishing TCP three-way handshakes for thousands of recurring metric requests adds unnecessary processing and state overhead.

Key Concept

TCP vs UDP Transport Characteristics and Application Protocol Mapping

Question 969Question →

An enterprise network administrator is implementing a Variable Length Subnet Masking (VLSM) scheme using the assigned summary prefix $172.28.128.0/18$ . The design requires allocating three subnets sequentially from the beginning of this address space, prioritizing the largest requirements first:

- Subnet A (Data Center): requires support for at least $1,000$ usable host IP addresses.
- Subnet B (App Servers): requires support for at least $500$ usable host IP addresses.
- Subnet C (Management): requires support for at least $250$ usable host IP addresses.

After allocating these three subnets efficiently without leaving unallocated gaps between them, what is the valid usable host IPv4 address range for the next available subnet that can accommodate a dev/test segment requiring at least $120$ usable host IP addresses?

172.28.135.1

172.28.135.126

172.28.135.0

172.28.135.127

172.28.136.1

172.28.136.126

172.28.135.1

172.28.135.254

Show answer & explanation

Answer: $172.28.135.1$ to $172.28.135.126$

Answer

The valid usable host address range for the next available subnet is

172.28.135.1

172.28.135.126

Allocating subnets sequentially based on host requirements yields: Subnet A (

172.28.128.0/22

, ending at

172.28.131.255

), Subnet B (

172.28.132.0/23

, ending at

172.28.133.255

), and Subnet C (

172.28.134.0/24

, ending at

172.28.134.255

). The next block starts at

172.28.135.0

. For

120

usable hosts, a

/25

subnet (

126

usable hosts) is required, giving a usable IP host range of

172.28.135.1

172.28.135.126

Step-by-Step Solution

Calculate prefix length and boundary for Subnet A (

1,000

usable hosts)

2^{10} - 2 = 1,022 \ge 1,000 \implies /22

prefix (

1,024

total addresses). Allocated range:

172.28.128.0

172.28.131.255

A /22 subnet provides 1,022 usable hosts across 4 third-octet block values.

Calculate prefix length and boundary for Subnet B (

500

usable hosts)

2^9 - 2 = 510 \ge 500 \implies /23

prefix (

512

total addresses). Starting IP:

172.28.132.0

. Allocated range:

172.28.132.0

172.28.133.255

A /23 subnet provides 510 usable host addresses.

Calculate prefix length and boundary for Subnet C (

250

usable hosts)

2^8 - 2 = 254 \ge 250 \implies /24

prefix (

256

total addresses). Starting IP:

172.28.134.0

. Allocated range:

172.28.134.0

172.28.134.255

A /24 subnet provides 254 usable host addresses.

Determine the network address and usable host range for the dev/test subnet (

120

usable hosts)

Next available start address is

172.28.135.0

2^7 - 2 = 126 \ge 120 \implies /25

prefix. Subnet range:

172.28.135.0/25

. Usable host range:

172.28.135.1

172.28.135.126

A /25 prefix accommodates up to 126 usable hosts, excluding the network ID (.0) and broadcast address (.127).

Key Concept

Variable Length Subnet Masking (VLSM) host requirement sizing and sequential block allocation

Estimated Time:3m 0s

Question 970Question →

An enterprise network architect is migrating a primary data center from a traditional 3-Tier (Access-Aggregation-Core) hierarchy to a 2-Tier Spine-Leaf (Clos) architecture to better handle high-volume East-West microservices traffic. Which TWO statements correctly describe the design rules and operational characteristics of this Spine-Leaf topology? (Choose two.)

Select all that apply

Every leaf switch connects to every spine switch, but leaf switches do not connect directly to other leaf switches.

Equal-Cost Multi-Path (ECMP) routing is leveraged across Layer 3 links to utilize all available bandwidth concurrently between leaf and spine switches.

Spine switches operate as Layer 2 switches that rely on Spanning Tree Protocol (STP) to block redundant uplinks and isolate broadcast domains.

Enabling STP PortFast on interswitch trunk links between leaf and spine switches is recommended to eliminate convergence delays when adding new switches.

Show answer & explanation

Answer: Every leaf switch connects to every spine switch, but leaf switches do not connect directly to other leaf switches.; Equal-Cost Multi-Path (ECMP) routing is leveraged across Layer 3 links to utilize all available bandwidth concurrently between leaf and spine switches.

Answer

The correct statements are that every leaf switch connects to every spine switch without direct leaf-to-leaf connections, and that Equal-Cost Multi-Path (ECMP) routing is utilized to load-balance traffic across all available links.

In a 2-Tier Spine-Leaf design, the fabric forms a bipartite graph where every leaf switch connects to every spine switch, with no direct connections between switches of the same tier. Traffic between leaves passes through spine switches using Layer 3 routing and Equal-Cost Multi-Path (ECMP), enabling deterministic low-latency, active-active forwarding across all available links.

Step-by-Step Solution

Analyze physical connectivity rules in a 2-Tier Spine-Leaf (Clos) architecture.

Leaf switches connect to all spine switches in a full mesh (bipartite graph). Leaves do not connect to leaves, and spines do not connect to spines.

Ensures predictable latency where every access point is exactly two hops away from any other access point.

Evaluate control plane forwarding mechanisms between leaf and spine nodes.

Layer 3 routing protocols are implemented across interswitch links to enable Equal-Cost Multi-Path (ECMP).

ECMP enables active-active packet forwarding over all physical links, avoiding the link blocking penalties of traditional Layer 2 STP topologies.

Identify misconceptions regarding Layer 2 switching and PortFast configuration on interswitch links.

STP blocking and PortFast on trunk links are inappropriate for leaf-spine interconnects.

Layer 3 forwarding prevents STP loops organically, and applying PortFast on switch trunks risks bridging loops.

Key Concept

Spine-Leaf (Clos) Topology Connectivity Rules and ECMP Forwarding

Estimated Time:2m 0s

Question 971Question →

A network engineer is configuring a routed (Layer 3) EtherChannel between Switch-A and Switch-B using LACP.

Switch-A is configured with the following commands:
text
interface Port-channel 1
no switchport
ip address 10.1.1.1 255.255.255.252
!
interface range GigabitEthernet1/0/1 - 2
no switchport
channel-group 1 mode passive

When verifying the EtherChannel status on Switch-B, the engineer observes the following output from `show etherchannel summary`:
text
Flags: D - down P - bundled in port-channel
I - stand-alone s - suspended
R - Layer3 S - Layer2
U - in use

Group Port-channel Protocol Ports
------+-------------+-----------+-----------------------------------------------
1 Po1(SD) LACP Gi1/0/1(D) Gi1/0/2(D)

Which configuration change on Switch-B will successfully resolve the issue and convert Port-channel 1 into an operational Layer 3 link?

Configure 'no switchport' under interface Port-channel 1 and member interfaces GigabitEthernet1/0/1 - 2, and set 'channel-group 1 mode active' on the member interfaces.

Configure 'no switchport' under interface Port-channel 1 and member interfaces GigabitEthernet1/0/1 - 2, and set 'channel-group 1 mode passive' on the member interfaces.

Set 'switchport trunk native vlan 10' under interface Port-channel 1 and set 'channel-group 1 mode active' on member interfaces GigabitEthernet1/0/1 - 2.

Configure 'no switchport' under interface Port-channel 1 and set 'channel-group 1 mode desirable' on member interfaces GigabitEthernet1/0/1 - 2.

Show answer & explanation

Answer: Configure 'no switchport' under interface Port-channel 1 and member interfaces GigabitEthernet1/0/1 - 2, and set 'channel-group 1 mode active' on the member interfaces.

Answer

Configure 'no switchport' under interface Port-channel 1 and member interfaces GigabitEthernet1/0/1 - 2, and set 'channel-group 1 mode active' on the member interfaces.

To create a Layer 3 EtherChannel, the 'no switchport' command must be executed on the logical Port-channel interface as well as all physical member interfaces. Furthermore, because Switch-A is configured in LACP passive mode, Switch-B must be configured in LACP active mode ('channel-group 1 mode active') so that LACP control packets are actively sent to initiate port bundling.

Step-by-Step Solution

Analyze the 'show etherchannel summary' output on Switch-B.

The flags show Po1(SD) and member interfaces Gi1/0/1(D) Gi1/0/2(D). 'S' indicates Layer 2 operational state, and 'D' indicates Down state.

Layer 3 EtherChannels require explicit conversion using the 'no switchport' command on both the Port-channel logical interface and the physical member interfaces.

Evaluate the LACP negotiation mode requirements.

Switch-A is configured with 'channel-group 1 mode passive'.

LACP requires at least one participating switch to be in 'active' mode. Passive-to-passive mode matching will never initiate LACP control traffic, keeping the bundle down.

Determine the necessary configuration on Switch-B.

Apply 'no switchport' to interface Port-channel 1 and member interfaces, then assign 'channel-group 1 mode active' to member interfaces.

This establishes a Layer 3 interface ('R' flag) and enables LACP active negotiation to complement Switch-A's passive mode.

Key Concept

Layer 3 EtherChannel LACP Negotiation and CLI State Verification

Estimated Time:2m 0s

Question 972Question →

A network technician connects interface GigabitEthernet0/1 on Switch-A to interface GigabitEthernet0/1 on Switch-B using an Ethernet link. Switch-A retains its factory default interface configuration of `switchport mode dynamic auto`, while Switch-B is explicitly configured with `switchport mode dynamic desirable`. Which two operational conditions describe the resulting state of this interswitch link?

Select all that apply

The link successfully negotiates and operates as an 802.1Q trunk link.

Frames belonging to the native VLAN traverse the trunk link without an 802.1Q header tag by default.

The link operational mode defaults to an access port because dynamic auto refuses trunk establishment requests from dynamic desirable ports.

Spanning Tree Protocol PortFast is automatically enabled on the link once trunking negotiation completes.

Show answer & explanation

Answer: The link successfully negotiates and operates as an 802.1Q trunk link.; Frames belonging to the native VLAN traverse the trunk link without an 802.1Q header tag by default.

Answer

The link negotiates to operate as an 802.1Q trunk, and native VLAN frames cross the trunk link untagged by default.

When configuring interswitch trunking via DTP, combining `dynamic desirable` on one end with `dynamic auto` on the other results in successful 802.1Q trunk negotiation because `desirable` actively initiates the negotiation state while `auto` accepts it. Additionally, under IEEE 802.1Q standard operation, frames destined for the native VLAN (default VLAN 1) are transmitted across the trunk link without an added 802.1Q header tag.

Step-by-Step Solution

Evaluate the Dynamic Trunking Protocol (DTP) negotiation between dynamic auto and dynamic desirable modes.

Dynamic desirable actively initiates DTP negotiation, and dynamic auto listens and agrees to form a trunk. Thus, the operational mode becomes an 802.1Q trunk.

DTP operational logic forms a trunk whenever at least one side actively negotiates (desirable or trunk) and the opposite side is willing to negotiate (auto or desirable).

Analyze standard 802.1Q frame encapsulation mechanics for native VLAN traffic.

By default, VLAN 1 is the native VLAN, and standard 802.1Q trunking does not insert a 4-byte 802.1Q tag into frames matching the native VLAN.

IEEE 802.1Q specifies native VLAN traffic as untagged to maintain backwards compatibility with legacy non-trunking Ethernet devices.

Key Concept

DTP Mode Negotiation and 802.1Q Native VLAN Tagging Mechanics

Question 973Question →

A network interface with a MAC address of $7069.5\text{A}11.2233$ is configured on a subnet with the assigned IPv6 prefix $2001:\text{db8}:1000:\text{abc}::/64$ . The interface automatically generates its IPv6 addresses using IEEE EUI-64 format. Which two statements regarding the resulting IPv6 configuration on this interface are correct?

Select all that apply

The calculated EUI-64 interface identifier for the host is 7269:5aff:fe11:2233.

The complete global unicast address formed by the interface is 2001:db8:1000:abc:7269:5aff:fe11:2233.

The interface identifier is constructed as 7069:5aff:fe11:2233 because the first byte of the MAC address remains unmodified during EUI-64 generation.

The /64 prefix allows

2^{64} - 2

usable host addresses because IPv6 reserves the first address for network identification and the last address for broadcast.

Show answer & explanation

Answer: The calculated EUI-64 interface identifier for the host is 7269:5aff:fe11:2233.; The complete global unicast address formed by the interface is 2001:db8:1000:abc:7269:5aff:fe11:2233.

Answer

The two correct statements are that the calculated EUI-64 interface identifier is 7269:5aff:fe11:2233 and the complete global unicast address formed by the interface is 2001:db8:1000:abc:7269:5aff:fe11:2233.

The EUI-64 process inserts 0xFFFE between the OUI and vendor portion of the MAC address and flips the 7th bit of the first byte (from 0x70 to 0x72), resulting in the interface ID 7269:5aff:fe11:2233. Appending this to prefix 2001:db8:1000:abc::/64 generates the global unicast address 2001:db8:1000:abc:7269:5aff:fe11:2233.

Step-by-Step Solution

Insert FFFE into the 48-bit MAC address

Splitting MAC 70:69:5A:11:22:33 into 70:69:5A and 11:22:33 and inserting FFFE produces 70:69:5A:FF:FE:11:22:33.

EUI-64 formatting expands 48-bit MAC addresses to 64 bits by inserting 16 bits (0xFFFE) in the middle.

Invert the Universal/Local (7th) bit of the first octet

First octet 0x70 in binary is 0111 0000. Inverting the 7th bit yields 0111 0010, which is 0x72 in hex. The interface ID becomes 7269:5aff:fe11:2233.

IEEE EUI-64 standards invert the 7th bit to reflect local scope management in IPv6 host addresses.

Combine prefix and EUI-64 interface ID

2001:db8:1000:abc::/64 + 7269:5aff:fe11:2233 = 2001:db8:1000:abc:7269:5aff:fe11:2233.

The subnet prefix forms the upper 64 bits and the EUI-64 ID forms the lower 64 bits of the global unicast address.

Key Concept

EUI-64 Interface Identifier Generation and IPv6 Addressing

Question 974Question →

A Cisco Catalyst switch receives an Ethernet frame on ingress port GigabitEthernet0/1 with Source MAC address 0010.ab12.3456 and Destination MAC address 0020.cd78.90ab. The switch's current MAC address table records 0010.ab12.3456 as learned on GigabitEthernet0/3, but has no entry for 0020.cd78.90ab. Which TWO actions will the switch perform upon processing this ingress frame? (Select two.)

Select all that apply

Update the MAC address table entry for 0010.ab12.3456 to associate it with port GigabitEthernet0/1.

Flood the frame out all operational ports within the same VLAN, excluding ingress port GigabitEthernet0/1.

Forward the frame directly out GigabitEthernet0/3 based on the previous MAC table entry for the host.

Drop the frame immediately because a MAC address security violation has occurred due to a station move.

Send an ICMP Redirect message back out GigabitEthernet0/1 to notify the sender of the topology update.

Show answer & explanation

Answer: Update the MAC address table entry for 0010.ab12.3456 to associate it with port GigabitEthernet0/1.; Flood the frame out all operational ports within the same VLAN, excluding ingress port GigabitEthernet0/1.

Answer

The switch updates the MAC address table entry for 0010.ab12.3456 to GigabitEthernet0/1 and floods the unknown unicast frame out all operational ports on the VLAN except GigabitEthernet0/1.

When an Ethernet frame arrives at a switch port, the switch first performs MAC address learning by checking the frame's source MAC address. If the source MAC address exists in the MAC table but is associated with a different interface, the switch updates the table entry with the new ingress port (station move update). Next, the switch looks up the frame's destination MAC address. Because the destination MAC address is not present in the MAC table, the switch treats the frame as unknown unicast and floods it out all active ports in the same VLAN except the receiving port.

Step-by-Step Solution

Examine the source MAC address handling (MAC Learning & Station Move).

The source MAC address 0010.ab12.3456 was previously listed on GigabitEthernet0/3. Since it arrived on GigabitEthernet0/1, the switch rewrites the table entry to associate 0010.ab12.3456 with GigabitEthernet0/1.

Layer 2 switches dynamically update dynamic MAC table entries whenever a known MAC address arrives on a different port.

Examine the destination MAC address handling (Forwarding Decision).

The destination MAC address 0020.cd78.90ab is missing from the MAC address table.

When a destination MAC address is not found in the Layer 2 forwarding table, the frame is classified as an unknown unicast frame.

Execute unknown unicast forwarding logic.

The frame is flooded to all active ports assigned to the same VLAN, except the receiving interface (GigabitEthernet0/1).

Unknown unicast traffic must be flooded across the broadcast domain so the intended destination host can receive it and respond.

Key Concept

Layer 2 MAC Table Station Learning and Unknown Unicast Flooding Mechanics

Question 975Question →

A network administrator assigns the IPv4 subnet mask $255.255.255.224$ to a VLAN interface on a Cisco switch. What is the maximum number of usable host IPv4 addresses that can be assigned to end devices in this subnet?

Show answer & explanation

Answer: 30

Answer

The maximum number of usable host IPv4 addresses is 30.

A subnet mask of

255.255.255.224

corresponds to a CIDR prefix of /27, leaving 5 bits for host addressing. Using the formula

2^n - 2

(where

n = 5

), the calculation yields

2^5 - 2 = 32 - 2 = 30

usable host IP addresses.

Step-by-Step Solution

Determine the number of host bits (

n

) available in the

255.255.255.224

subnet mask.

The mask has 27 network bits and 5 host bits (

32 - 27 = 5

The last octet value

224

in binary is

11100000_2

, meaning 3 bits belong to the network/subnet portion and 5 bits belong to the host portion.

Calculate the number of usable host IP addresses using the formula

2^n - 2

2^5 - 2 = 32 - 2 = 30

usable host addresses.

The formula

2^n - 2

accounts for the total IP addresses (

2^n

) minus the reserved network identifier (all host bits set to 0) and the broadcast address (all host bits set to 1).

Key Concept

Usable Host Address Calculation

Question 976Question →

A network engineer is designing a wireless LAN for a multi-story corporate building and must account for radio frequency (RF) propagation differences between the $2.4\text{ GHz}$ and $5\text{ GHz}$ bands. Which two statements accurately describe the physical characteristics and channel allocations of these frequency bands? (Select two.)

Select all that apply

The

2.4\text{ GHz}

frequency band experiences lower free-space path loss and attenuates less through physical walls, resulting in a larger coverage area per access point.

The

5\text{ GHz}

frequency band provides a significantly greater number of non-overlapping

20\text{ MHz}

channels than the

2.4\text{ GHz}

band, which helps minimize co-channel interference in high-density enterprise environments.

The

2.4\text{ GHz}

frequency band supports up to 24 non-overlapping

20\text{ MHz}

channels, making it preferable for high-density deployment of real-time voice applications.

Higher frequency signals in the

5\text{ GHz}

band penetrate dense building materials such as concrete and brick more effectively than

2.4\text{ GHz}

signals.

The

2.4\text{ GHz}

spectrum is immune to non-802.11 interference because it operates exclusively within licensed frequency ranges.

Show answer & explanation

Answer: The $2.4\text{ GHz}$ frequency band experiences lower free-space path loss and attenuates less through physical walls, resulting in a larger coverage area per access point.; The $5\text{ GHz}$ frequency band provides a significantly greater number of non-overlapping $20\text{ MHz}$ channels than the $2.4\text{ GHz}$ band, which helps minimize co-channel interference in high-density enterprise environments.

Answer

The correct statements are that the 2.4 GHz band experiences lower free-space path loss and penetrates physical walls better (providing a larger coverage area per AP), and the 5 GHz band provides significantly more non-overlapping 20 MHz channels to mitigate co-channel interference.

The 2.4 GHz band uses longer wavelengths, giving it superior range and obstacle penetration through walls compared to 5 GHz. Additionally, the 5 GHz band provides up to 24 non-overlapping 20 MHz channels in North America (UNII bands), which provides significantly higher capacity and reduces co-channel interference (CCI) compared to the limited 3 non-overlapping channels (1, 6, 11) available in the 2.4 GHz band.

Step-by-Step Solution

Analyze the RF propagation characteristics of 2.4 GHz versus 5 GHz frequency bands.

Lower frequencies (2.4 GHz) have longer wavelengths, yielding lower free-space loss and superior penetration through physical structures relative to higher frequencies (5 GHz).

RF signal attenuation increases as frequency increases.

Evaluate the channel availability for both frequency bands in enterprise WLAN design.

The 2.4 GHz spectrum has only 3 non-overlapping 20 MHz channels (1, 6, 11), whereas 5 GHz provides up to 24 non-overlapping channels across UNII-1, UNII-2 (DFS), and UNII-3 bands.

Greater channel availability allows high-density access point deployments without co-channel interference (CCI).

Key Concept

RF Propagation and Channel Allocation Differences (2.4 GHz vs 5 GHz)

Question 977Question →

A network engineer is configuring network topology discovery across a multi-vendor environment containing both Cisco and non-Cisco switches. Which IEEE standard defines the open, vendor-neutral Layer 2 discovery protocol used to identify neighboring devices?

IEEE 802.1AB

IEEE 802.1Q

IEEE 802.1D

IEEE 802.3ad

Show answer & explanation

Answer: IEEE 802.1AB

Answer

IEEE 802.1AB is the IEEE standard that defines Link Layer Discovery Protocol (LLDP).

The IEEE 802.1AB standard formally defines Link Layer Discovery Protocol (LLDP). LLDP allows network devices to advertise identity, capabilities, and neighbor information across heterogeneous multi-vendor networks.

Step-by-Step Solution

Identify the protocol requirements from the scenario

The scenario calls for an open, vendor-neutral Layer 2 discovery protocol usable across multi-vendor equipment.

Cisco Discovery Protocol (CDP) is Cisco-proprietary, whereas Link Layer Discovery Protocol (LLDP) is open-standard.

Map LLDP to its governing IEEE standard specification

LLDP is standardized under IEEE 802.1AB.

IEEE 802.1AB specifies the Type-Length-Value (TLV) frame format and operational procedures for LLDP.

Key Concept

Link Layer Discovery Protocol (LLDP) IEEE standard identification

Question 978Question →

A network engineer analyzes a packet capture of an active application stream during heavy network load. The capture reveals that the receiving host continuously updates the 16-bit Window field in its acknowledgment segments to smaller values, causing the sending host to reduce the amount of unacknowledged data sent before waiting for an ACK. Which statement correctly identifies this transport layer mechanism and its operational contrast with UDP?

TCP employs dynamic windowing for receiver-driven flow control to prevent buffer overflow, whereas UDP lacks flow control mechanisms and a window size header field entirely.

TCP uses the window field to perform intermediate router rate limiting, whereas UDP relies on its 8-byte header to sequence packets and request retransmissions.

TCP windowing triggers automatic segment retransmission upon packet corruption, whereas UDP uses a variable 20-byte header to negotiate transmission window sizes.

TCP reduces the window size to signal Path MTU Discovery (PMTUD) updates, whereas UDP provides sequence tracking to manage buffer exhaustion without acknowledgments.

Show answer & explanation

Answer: TCP employs dynamic windowing for receiver-driven flow control to prevent buffer overflow, whereas UDP lacks flow control mechanisms and a window size header field entirely.

Answer

TCP employs dynamic windowing for receiver-driven flow control to prevent buffer overflow, whereas UDP lacks flow control mechanisms and a window size header field entirely.

The correct answer accurately describes TCP flow control. The TCP header includes a 16-bit Window field that allows the receiving host to advertise its available buffer space. As the buffer fills, the receiver reduces the window size, instructing the sender to transmit less data before awaiting an ACK. In contrast, UDP has a simple, fixed 8-byte header (Source Port, Destination Port, Length, Checksum) and does not provide flow control, windowing, or rate management.

Step-by-Step Solution

Analyze the observed protocol behavior in the packet capture.

The receiver is modifying the 16-bit Window field in acknowledgment segments to restrict the sender's unacknowledged data output.

This behavior is known as dynamic windowing (sliding window flow control), which protects receiver buffers from being overwhelmed.

Compare TCP header capabilities with UDP header structure.

TCP headers (minimum 20 bytes) contain fields for Sequence Number, Acknowledgment Number, and Window Size. UDP headers (fixed 8 bytes) contain only Source Port, Destination Port, Length, and Checksum.

UDP is connectionless and stateless, prioritizing low overhead and speed over flow control, sequencing, or error recovery.

Evaluate the option choices based on transport layer mechanics.

The option identifying TCP receiver-driven flow control and UDP's complete lack of windowing and flow control is the only technically accurate comparison.

UDP leaves application-level buffer management entirely to upper-layer protocols if needed.

Key Concept

TCP Sliding Window Flow Control vs. UDP Stateless Header Overhead

Estimated Time:2m 0s

Question 979Question →

A network administrator is deploying a virtualized server environment using bare-metal Type 1 hypervisors connected to an enterprise campus network. Which two operational roles and functions are performed directly by the Type 1 hypervisors in this infrastructure? (Select two.)

Select all that apply

Abstracting underlying physical hardware resources to allocate vCPUs, system memory, and virtual network interfaces directly to hosted virtual machines

Facilitating Layer 2 frame forwarding between virtual machines residing on the same physical host via an embedded virtual switch

Operating as an application software layer on top of an existing general-purpose host operating system such as Windows Server or Linux

Terminating Layer 3 broadcast domains and making IP packet forwarding decisions between subnets across physical servers

Show answer & explanation

Answer: Abstracting underlying physical hardware resources to allocate vCPUs, system memory, and virtual network interfaces directly to hosted virtual machines; Facilitating Layer 2 frame forwarding between virtual machines residing on the same physical host via an embedded virtual switch

Answer

The two correct functions performed directly by a Type 1 hypervisor are abstracting physical hardware resources to allocate vCPUs, memory, and virtual network interfaces to guest virtual machines, and facilitating Layer 2 frame forwarding between virtual machines on the same physical host through an integrated virtual switch.

Type 1 bare-metal hypervisors run directly on server hardware, allowing efficient hardware abstraction and direct distribution of vCPU, memory, and virtual interfaces to guest VMs. In addition, hypervisors feature built-in Layer 2 virtual switches (vSwitches) to forward frames locally between virtual machines sharing the same physical host.

Step-by-Step Solution

Identify the architectural deployment model of a Type 1 hypervisor.

A Type 1 hypervisor runs directly on the bare-metal physical hardware without relying on a underlying general-purpose host operating system.

This bare-metal positioning gives the hypervisor direct control over hardware virtualization.

Analyze the resource management and network forwarding capabilities built into the hypervisor.

The hypervisor partitions physical CPU, RAM, and NICs into virtual components for VMs and includes a virtual switch (vSwitch) to forward Layer 2 frames locally.

Local VM-to-VM traffic within the same host is bridged at Layer 2 by the internal vSwitch, while inter-subnet Layer 3 routing is handed off to network infrastructure devices.

Key Concept

Type 1 hypervisor bare-metal architecture and virtual switching roles

Question 980Question →

During the standard EUI-64 process used to derive a 64-bit IPv6 interface identifier from a 48-bit MAC address, what 16-bit hexadecimal value is inserted into the middle of the MAC address?

Show answer & explanation

Answer: FFFE; fffe; 0xFFFE; 0xfffe

Answer

FFFE

To create a 64-bit interface identifier using the IEEE EUI-64 format, a host takes its 48-bit MAC address, splits it into two 24-bit halves (OUI and NIC identifier), and inserts the 16-bit hexadecimal value FFFE (0xFFFE) in the middle. Additionally, the 7th bit (Universal/Local bit) of the first byte is inverted.

Step-by-Step Solution

Split the 48-bit MAC address into two equal 24-bit halves

The first 24 bits represent the Organizationally Unique Identifier (OUI) and the last 24 bits represent the Extension Identifier.

EUI-64 modification requires inserting a specific 16-bit sequence between these two halves.

Insert the 16-bit value FFFE into the midpoint between the two 24-bit halves

The 48-bit address expands to a 64-bit value containing FFFE in the center.

Inserting 0xFFFE creates the mandatory 64-bit structure required for an EUI-64 interface identifier.

Key Concept

EUI-64 Interface Identifier Generation

PreviousPage 49 / 100Next

All practice questions

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept