All practice questions

2237 questions

All types2,237 Multiple choice1,150 Multiple select488 Numeric30 Matching350 Ordering201 Short answer18

When configuring Network Address Translation (NAT) on a gateway router, which term specifically describes the private IP address assigned to an internal host before any address translation occurs?

Inside local

Inside global

Outside local

Outside global

Show answer & explanation

Answer: Inside local

Answer

Inside local is the term used to describe the private IP address assigned to an internal network host before translation.

The term 'inside local' refers to the IP address assigned to a host on the internal network before NAT performs any address translation. This is typically a private IPv4 address from RFC 1918 ranges.

Step-by-Step Solution

Identify the location of the host (internal vs. external).

The host is located on the internal network, requiring an 'Inside' designation.

Standard NAT terminology uses 'Inside' for devices located within the private organizational network boundary.

Determine whether the address is pre-translation or post-translation.

The address is prior to translation, making it a 'Local' address.

'Local' addresses represent un-translated addresses as seen from inside the network.

Key Concept

NAT Address Terminology (Inside Local, Inside Global, Outside Local, Outside Global)

Question 242Question →

A network technician connects five workstations and two servers directly to individual full-duplex ports on a managed Layer 2 switch. Three of the active ports are assigned to VLAN 15, and the remaining four active ports are assigned to VLAN 35. No Layer 3 routing device is present on the network. How many collision domains and broadcast domains exist on this switch?

7 collision domains and 2 broadcast domains

1 collision domain and 2 broadcast domains

7 collision domains and 7 broadcast domains

2 collision domains and 7 broadcast domains

Show answer & explanation

Answer: 7 collision domains and 2 broadcast domains

Answer

7 collision domains and 2 broadcast domains

Each connected port on a Layer 2 Ethernet switch operating in full-duplex mode constitutes an independent collision domain, yielding 7 collision domains for the 7 active host ports. Broadcast domains are defined by VLAN boundaries; because the switch is partitioned into VLAN 15 and VLAN 35, there are exactly 2 broadcast domains.

Step-by-Step Solution

Count the total number of active switch ports to determine collision domains

5 workstations + 2 servers = 7 connected switch ports, producing 7 distinct collision domains

Layer 2 switches isolate collision domains on a per-port basis when running in full-duplex mode.

Count the total number of configured VLANs to determine broadcast domains

VLAN 15 and VLAN 35 represent 2 distinct logical VLANs, producing 2 broadcast domains

A Virtual Local Area Network (VLAN) logically segments a physical switch into separate Layer 2 broadcast domains.

Key Concept

Collision and Broadcast Domain Segmentation in Layer 2 Switches

Question 243Question →

When a non-root switch determines which interface will serve as its Root Port, it processes incoming Bridge Protocol Data Units (BPDUs) using a specific sequence of decision criteria. Place the steps taken by the switch in the correct operational order from first to last.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence for Root Port selection is: 1) Receive BPDUs and read advertised Root Path Cost, 2) Add local interface cost to calculate cumulative path cost, 3) Select the port with the lowest total path cost, and 4) Use tie-breaker criteria (lowest designated Bridge ID and Port ID) if path costs are equal.

The Spanning Tree Protocol (STP) Root Port selection mechanism follows a strict decision hierarchy: receiving neighbor advertised path costs first, adding the local interface cost to calculate total path cost second, choosing the lowest total path cost third, and resolving any ties using designated Bridge ID and Port ID values last.

Step-by-Step Solution

Ingest BPDUs

The switch reads the incoming BPDU frame fields, specifically obtaining the advertised Root Path Cost from adjacent switches.

Path cost evaluations cannot begin until advertised values are collected from neighbors.

Calculate Cumulative Path Cost

For each candidate port, local port path cost is added to the advertised cost.

STP calculates path cost inbound at the receiving switch port based on link speed.

Evaluate Lowest Path Cost

The candidate port offering the lowest overall path cost to the root bridge is identified.

Lowest total path cost is the primary decision factor for Root Port designation.

Evaluate Tie-Breakers

If a tie exists, the switch compares neighbor Bridge IDs, then neighbor Port IDs, to break the tie.

Tie-breaker fields exist to ensure a deterministic selection when multiple paths cost the same.

Key Concept

Spanning Tree Protocol (STP) Root Port Decision Sequence

Question 244Question →

Match each network topology classification to its defining structural characteristic and operational failure profile.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Bus Topology matches the shared continuous trunk cable with terminators; Ring Topology matches the sequential circular token path vulnerable to single node failure; Full Mesh Topology matches complete point-to-point node connections calculated by

n(n-1)/2

; Star Topology matches connections radiating from a central device where single link breaks only isolate one node.

The matches accurately pair each physical topology with its physical layout and failure domain behavior. Bus topologies rely on a terminated single backbone line. Ring topologies process traffic sequentially in a circular loop. Full mesh topologies link every device pair for total redundancy. Star topologies isolate individual drop cables through a central distribution device.

Step-by-Step Solution

Analyze Bus Topology characteristics

Identified that bus topologies utilize a central backbone cable terminated on both ends, where a break affects all nodes.

Bus networks rely on shared physical media continuity.

Analyze Ring Topology characteristics

Identified that ring topologies pass data sequentially in a circle from one device to the next.

Without redundant rings, an outage at any intermediary host breaks the circuit.

Analyze Full Mesh Topology characteristics

Identified that full mesh requires dedicated links between every node pair, adhering to the mathematical formula

L = \frac{n(n-1)}{2}

Full mesh offers maximum fault tolerance due to full point-to-point redundancy.

Analyze Star Topology characteristics

Identified that star topology connects hosts independently to a central switch or hub.

Failure of an edge cable impacts only the single connected endpoint.

Key Concept

Physical Network Topologies and Fault Tolerance Profiles

Estimated Time:1m 30s

Question 245Question →

Match each Network Address Translation (NAT) term on the left with its corresponding definition or role on the right.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Inside Local Address corresponds to the private IPv4 address on the local endpoint. Inside Global Address corresponds to the public IPv4 address representing an internal endpoint to external networks. Outside Global Address corresponds to the external target's public IPv4 address. Port Address Translation (PAT) corresponds to mapping multiple private hosts to a single public IP address using distinct port numbers.

Each NAT concept strictly aligns with standard networking terminology: Inside Local is the internal host's private IP, Inside Global is the internal host's public translated IP, Outside Global is the external host's public IP, and Port Address Translation (PAT) multiplexes multiple private IP addresses over a single public IP using Layer 4 port numbers.

Step-by-Step Solution

Identify the boundary and visibility of internal addresses

Inside Local is private to the internal network, whereas Inside Global is public and visible to the Internet.

CompTIA Network+ standard definitions differentiate between local (private side) and global (public side) address perspectives.

Identify the external destination address terminology

Outside Global represents the public address of the remote host on the internetwork.

Outside addresses refer to devices located outside the local administrative domain, with global indicating its appearance on the public Internet.

Identify the translation mechanism utilizing Layer 4 identifiers

Port Address Translation (PAT) leverages TCP/UDP port numbers to multiplex connections.

PAT dynamically maps thousands of internal private IP addresses to a single public IP address by tracking unique port mappings.

Key Concept

NAT Terminology and PAT Overload Operation

Question 246Question →

A server receives an incoming network transmission where an HTTP request payload is encapsulated within a TCP segment, an IPv4 packet, and an Ethernet frame. As the destination host's operating system stack performs de-encapsulation at the Transport layer (Layer 4), which header field is inspected to deliver the inner payload to the correct server process?

Destination Port Number

Protocol field

EtherType field

Source Port Number

Show answer & explanation

Answer: Destination Port Number

Answer

The destination port number in the Transport layer header is inspected by the receiving network stack to direct the payload to the appropriate listening application service.

During the de-encapsulation process, each layer of the OSI model inspects its corresponding header to determine how to route the inner Protocol Data Unit (PDU) upward. At the Transport layer (Layer 4), TCP or UDP headers contain a Destination Port field. The host OS reads this destination port to direct the segment's data payload to the exact application service bound to that port.

Step-by-Step Solution

Analyze the incoming data flow during de-encapsulation.

The physical network interface accepts the electrical/optical signals and strips the Layer 2 Ethernet header after checking the frame header and EtherType field.

The EtherType field notifies Layer 2 that the encapsulated payload belongs to Network layer IPv4.

Evaluate Network layer (Layer 3) processing.

The IP protocol stack inspects the destination IP address and the Protocol field within the IPv4 header.

The Protocol field specifies that the payload should be handed off to TCP at Layer 4.

Evaluate Transport layer (Layer 4) de-encapsulation.

The TCP protocol stack receives the segment and inspects the Destination Port Number in the TCP header.

The destination port number acts as the address identifier for the specific application socket listening on the server.

Key Concept

De-encapsulation and Layer 4 Port Multiplexing

Question 247Question →

A network administrator is reconfiguring a branch office network segment. The segment currently contains $118$ desktop computers, $6$ network printers, and $2$ router interface gateways. System monitoring indicates upcoming team expansion will require an additional $8$ IP addresses next month. If the administrator wants to use the smallest possible IPv4 subnet mask that accommodates all current and projected devices while reserving required network and broadcast addresses, which CIDR notation subnet mask should be applied?

/25

/24

/23

/26

Show answer & explanation

Answer: /24

Answer

/24

The total number of required usable host IP addresses is calculated as

118 + 6 + 2 + 8 = 134

. To determine the smallest suitable subnet, we apply the formula

2^h - 2 \ge 134

, where

h

is the number of host bits. A subnet with

h = 7

bits (/25) yields

2^7 - 2 = 126

usable host addresses, which falls short. Increasing host bits to

h = 8

bits (/24) yields

2^8 - 2 = 254

usable host addresses, which fully accommodates all 134 devices without unnecessary over-allocation.

Step-by-Step Solution

Calculate total host IP addresses required.

Current devices:

118 + 6 + 2 = 126

hosts. With projected growth:

126 + 8 = 134

host IP addresses needed.

All active interfaces and future devices require unique usable host IP addresses on the network segment.

Determine the required host bits (

h

) using the usable host formula

2^h - 2 \ge 134

For

h = 7

2^7 - 2 = 126

usable hosts (insufficient). For

h = 8

2^8 - 2 = 254

usable hosts (sufficient).

Subnet calculations must subtract 2 addresses (

2^h - 2

) to reserve the network ID and broadcast address.

Calculate the CIDR prefix from the host bits.

CIDR prefix =

32 - 8 = /24

An IPv4 address consists of 32 bits, so subtracting 8 host bits leaves 24 network prefix bits.

Key Concept

IPv4 CIDR Subnetting and Usable Host Address Calculation

Question 248Question →

Which autoconfiguration mechanism allows an IPv6 host to dynamically generate its own unicast IP address using network prefix information received in Router Advertisement (RA) messages without requiring a stateful DHCP server?

Show answer & explanation

Answer: SLAAC; Stateless Address Autoconfiguration; stateless address autoconfiguration

Answer

SLAAC (Stateless Address Autoconfiguration)

SLAAC (Stateless Address Autoconfiguration) allows an IPv6 client to automatically generate its own globally unique or link-local address by combining the IPv6 prefix provided by a local router via ICMPv6 Router Advertisement (RA) messages with a locally derived 64-bit interface identifier (such as EUI-64 or random privacy address).

Step-by-Step Solution

Identify the IPv6 address assignment requirement

The scenario describes dynamic host address generation using Router Advertisement (RA) messages without a stateful DHCP server.

IPv6 introduces a native mechanism for hosts to autoconfigure network layer parameters directly from local router advertisements.

Match the protocol mechanism to its standardized term

Stateless Address Autoconfiguration (SLAAC) is the protocol mechanism that combines the advertised network prefix with an interface identifier.

SLAAC requires no state management on a central server, distinguishing it from stateful DHCPv6.

Key Concept

Stateless Address Autoconfiguration (SLAAC)

Estimated Time:45s

Question 249Question →

In a layer 2 switched network running IEEE 802.1D Spanning Tree Protocol (STP), Switch-A is elected as the Root Bridge. Switch-D is evaluating its path options to reach Switch-A and receives BPDUs on two separate interfaces:

- Interface GigabitEthernet0/1 connects to Switch-B (Bridge ID $32768\text{:0000.0000.000B}$ ). Switch-B advertises a Root Path Cost of $4$ . The link speed between Switch-D and Switch-B is $1\text{ Gbps}$ (path cost $4$ ).
- Interface GigabitEthernet0/2 connects to Switch-C (Bridge ID $32768\text{:0000.0000.000A}$ ). Switch-C advertises a Root Path Cost of $4$ . The link speed between Switch-D and Switch-C is $1\text{ Gbps}$ (path cost $4$ ).

Which interface on Switch-D will be selected as the Root Port, and what is the primary reason for this selection?

GigabitEthernet0/2, because both paths yield an identical total Root Path Cost of 8, and Switch-C presents a lower Designated Bridge ID than Switch-B.

GigabitEthernet0/1, because Switch-B has a higher MAC address numerical value, which gives it higher election precedence when path costs are equal.

GigabitEthernet0/1, because traffic over untagged native VLAN trunks is automatically directed to the switch with the higher MAC address to resolve forwarding conflicts.

Both GigabitEthernet0/1 and GigabitEthernet0/2, because STP automatically places ports with equal cumulative path costs into the Forwarding state for Layer 2 load balancing.

Show answer & explanation

Answer: GigabitEthernet0/2, because both paths yield an identical total Root Path Cost of 8, and Switch-C presents a lower Designated Bridge ID than Switch-B.

Answer

GigabitEthernet0/2 will be selected as the Root Port because both paths result in an equal total Root Path Cost of 8, and Switch-C provides a lower Designated Bridge ID (ending in 000A) compared to Switch-B (ending in 000B).

When a switch calculates paths to the Root Bridge, it evaluates decision criteria in strict order: 1) Lowest cumulative Root Path Cost, 2) Lowest upstream Designated Bridge ID, 3) Lowest upstream Designated Port ID, and 4) Lowest local Port ID. In this scenario, both paths yield an identical total path cost of 8. The tie is broken by comparing the Designated Bridge IDs of Switch-B and Switch-C. Switch-C has a lower MAC address (0000.0000.000A) than Switch-B (0000.0000.000B), making GigabitEthernet0/2 the Root Port.

Step-by-Step Solution

Calculate the cumulative Root Path Cost for each receiving interface on Switch-D.

Path via Switch-B = 4 (advertised by Switch-B) + 4 (Gigabit link cost) = 8. Path via Switch-C = 4 (advertised by Switch-C) + 4 (Gigabit link cost) = 8.

STP first compares total root path costs to identify the shortest path to the Root Bridge.

Evaluate the STP decision criteria tiebreaker since cumulative path costs are equal.

Compare upstream Designated Bridge IDs: Switch-B (

32768\text{:0000.0000.000B}

) vs Switch-C (

32768\text{:0000.0000.000A}

When cumulative root path costs are equal, the tiebreaker is the lowest upstream Designated Bridge ID.

Determine the winning interface.

Switch-C has the lower MAC address (

0000.0000.000A < 0000.0000.000B

), so interface GigabitEthernet0/2 is selected as the Root Port.

Lower numerical Bridge ID values have higher priority in STP calculations.

Key Concept

STP Root Port Selection Criteria and Tiebreakers

Estimated Time:1m 30s

Question 250Question →

A network engineer is partitioning the address block $10.45.160.0/19$ to provision a new VoIP network segment that must accommodate at least $500$ IP phones. To prevent address space depletion, the engineer allocates the smallest valid subnet starting at the beginning of the block that satisfies this host capacity requirement. What is the last usable host IP address of this newly allocated subnet?

10.45.161.255

10.45.160.254

10.45.161.254

10.45.163.254

Show answer & explanation

Answer: 10.45.161.254

Answer

10.45.161.254

To accommodate at least

500

usable host addresses with minimal wastage,

9

host bits are needed (

2^9 - 2 = 510

usable addresses), establishing a

/23

subnet mask. The first

/23

subnet within

10.45.160.0/19

ranges from

10.45.160.0

(Network ID) to

10.45.161.255

(Broadcast Address). Subtracting

1

from the broadcast address yields

10.45.161.254

as the final usable host IP address.

Step-by-Step Solution

Determine the required host bits and CIDR prefix length

9 host bits are required, yielding a /23 subnet prefix

The formula for usable hosts is

2^h - 2 \ge 500

. For

h = 8

2^8 - 2 = 254

(insufficient). For

h = 9

2^9 - 2 = 510

(sufficient). The prefix length is

32 - 9 = 23

Calculate the network block boundaries for the first /23 subnet

Network ID: 10.45.160.0/23, Broadcast Address: 10.45.161.255

A /23 subnet has a block size of

2

in the third octet (

256 - 254 = 2

). Starting at

10.45.160.0

, the network spans from

10.45.160.0

through

10.45.161.255

Identify the last usable host IP address within the subnet boundary

10.45.161.254

The last usable host IP address is always one numeric value below the broadcast address (

10.45.161.255 - 1 = 10.45.161.254

Key Concept

Subnet Host Capacity and Subnet Boundary Calculation

Estimated Time:2m 0s

Question 251Question →

An engineer is mapping network service traffic for perimeter security monitoring. Match each network protocol on the left with its standard default port number and transport layer protocol on the right.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Server Message Block (SMB) matches Port 445 / TCP; Internet Message Access Protocol (IMAP) matches Port 143 / TCP; SNMP Trap notifications match Port 162 / UDP; Network Time Protocol (NTP) matches Port 123 / UDP.

Each protocol is accurately matched to its assigned IANA default port number and transport layer protocol: SMB uses TCP port 445, IMAP uses TCP port 143, SNMP traps use UDP port 162, and NTP uses UDP port 123.

Step-by-Step Solution

Identify transport requirements for connection-oriented file sharing and email retrieval protocols.

SMB requires reliable TCP transmission over port 445, and standard IMAP requires TCP over port 143.

File transfers and email access require connection-oriented transport guarantees provided by TCP.

Identify transport requirements for time synchronization and asynchronous trap alert protocols.

NTP uses lightweight connectionless UDP port 123, and SNMP Traps use UDP port 162 to deliver event messages to management systems.

Time synchronization and automated agent traps rely on low-overhead UDP transport.

Key Concept

Standard default port numbers and transport layer protocols (TCP/UDP) for enterprise networking services.

Question 252Question →

An enterprise network engineering team is deploying IPv6 across a new corporate VLAN. The design requirements mandate that client endpoints dynamically auto-configure their Global Unicast Address (GUA) interface identifiers using SLAAC and EUI-64 from the prefix advertised by the local default gateway. Additionally, clients must receive additional network settings—specifically IPv6 DNS server addresses and domain search lists—from a central DHCPv6 server without creating or tracking stateful IPv6 address leases on the DHCPv6 server. During initial deployment verification, client workstations correctly construct their GUA and link-local addresses but fail to receive any DNS configuration from the network. Which Router Advertisement (RA) flag configuration on the local default gateway router interface must be applied to resolve this issue?

Set the Managed Address Configuration flag (M flag) to 0 and the Other Stateful Configuration flag (O flag) to 1 on the router interface.

Set the Managed Address Configuration flag (M flag) to 1 and the Other Stateful Configuration flag (O flag) to 1, while defining the server's DHCPv6 pool range using multiple double-colon zero compressions such as 2001:db8::1::50.

Deploy an IPv6 DNS server and configure a standard DNS A record on the DNS server to map host IPv6 GUAs to hostnames.

Set the Managed Address Configuration flag (M flag) to 1 and the Other Stateful Configuration flag (O flag) to 0, while assigning the host default gateway address to a non-local IPv4 subnet address.

Show answer & explanation

Answer: Set the Managed Address Configuration flag (M flag) to 0 and the Other Stateful Configuration flag (O flag) to 1 on the router interface.

Answer

The local router interface must be configured with the Managed Address Configuration flag (M flag) set to 0 and the Other Stateful Configuration flag (O flag) set to 1.

Stateless DHCPv6 allows client endpoints to auto-configure their own IPv6 Global Unicast Address via SLAAC while contacting a DHCPv6 server for additional network options like DNS. This behavior is enabled on the network segment by sending ICMPv6 Router Advertisements with the Managed Address Configuration flag (M flag) cleared (0) and the Other Stateful Configuration flag (O flag) set (1).

Step-by-Step Solution

Analyze the autoconfiguration requirement for host addresses.

Hosts must use SLAAC with EUI-64 to derive their Global Unicast Address from the advertised prefix.

The requirement specifies dynamic self-generation of address interface identifiers without stateful address tracking.

Evaluate the Router Advertisement (RA) Managed Address Configuration flag (M flag).

The M flag must be set to 0 (disabled).

An M flag value of 0 signals to client hosts that IPv6 addresses are not available via stateful DHCPv6 and must be acquired through SLAAC.

Evaluate the Router Advertisement (RA) Other Stateful Configuration flag (O flag).

The O flag must be set to 1 (enabled).

An O flag value of 1 informs client hosts to use Stateless DHCPv6 to obtain supplementary configuration information (such as DNS server addresses and domain search names) while keeping address generation under SLAAC.

Key Concept

IPv6 Stateless DHCPv6 Configuration via Router Advertisement Flags (M flag = 0, O flag = 1)

Question 253Question →

A network administrator is troubleshooting an OSPF dynamic routing issue between two core routers connected via a point-to-point Gigabit Ethernet link. Router 1 has its interface configured with an MTU of $1500$ bytes, while Router 2 has its interface configured with an MTU of $1492$ bytes. Both interfaces share the same $/30$ subnet, OSPF Area $0$ , Hello timer of $10$ seconds, and Dead timer of $40$ seconds. When reviewing the OSPF neighbor status on Router 1, the neighbor relationship remains stuck in the EXSTART/EXCHANGE state. Which of the following identifies the root cause of this neighbor state condition?

The routers cannot negotiate master/slave roles or transmit Database Description (DBD) packets due to the MTU size mismatch.

The OSPF Hello packets are dropped at Layer 2 because of mismatched PDU frame encapsulation types across the physical link.

The Hello and Dead timers are mismatched, preventing the routers from establishing basic bi-directional communication.

The routers are attempting to create an automated PAT overload session across the point-to-point connection.

Show answer & explanation

Answer: The routers cannot negotiate master/slave roles or transmit Database Description (DBD) packets due to the MTU size mismatch.

Answer

An MTU mismatch between adjacent router interfaces prevents the successful exchange of Database Description (DBD) packets, causing the OSPF neighbor state machine to stall in the EXSTART/EXCHANGE state.

The correct answer identifies that an MTU mismatch between adjacent OSPF router interfaces causes the neighbor state machine to become stuck in the EXSTART/EXCHANGE state. During EXSTART, routers elect master/slave roles and begin exchanging Database Description (DBD) packets containing interface MTU values. If the MTU values do not match, the routers cannot complete the DBD summary exchange and fail to transition to the LOADING or FULL states.

Step-by-Step Solution

Analyze the OSPF neighbor state machine progression.

The routers successfully reached the 2-WAY state (evidenced by reaching EXSTART), confirming that IP connectivity, subnets, Area IDs, and Hello/Dead timers match.

If basic parameters like timers or subnets were mismatched, the neighbor relationship would remain in the DOWN or INIT state.

Evaluate the function of the EXSTART/EXCHANGE state.

In EXSTART/EXCHANGE, routers elect a primary (master) router using initial sequence numbers and exchange Database Description (DBD) packets describing their Link-State Databases (LSDB).

DBD packets include the interface MTU field to ensure both endpoints can exchange routing information summaries without fragmentation issues.

Determine the impact of the MTU discrepancy (

1500

bytes vs

1492

bytes).

Router 1 rejects incoming DBD packets from Router 2 or fails to receive DBD acknowledgments because the MTU values do not match.

By default, OSPF requires matching MTUs on connected interfaces; a mismatch causes DBD packet exchange failure, leaving the adjacency indefinitely stuck in EXSTART/EXCHANGE.

Key Concept

OSPF Adjacency States and MTU Requirements

Question 254Question →

A network administrator is deploying a network of switches using the IEEE 802.1D Spanning Tree Protocol (STP). Currently, all switches share the default bridge priority value of $32768$ . Which configuration change on a specific switch will force it to be elected as the STP root bridge?

Decreasing the bridge priority value of the switch to a number lower than 32768

Increasing the bridge priority value of the switch to the maximum value of 65535

Assigning the highest numerical MAC address to the primary management interface of the switch

Changing the native VLAN on the switch trunk interfaces to an unused VLAN ID

Show answer & explanation

Answer: Decreasing the bridge priority value of the switch to a number lower than 32768

Answer

Decreasing the bridge priority value of the switch to a number lower than 32768 will ensure it has the lowest Bridge ID and becomes the STP root bridge.

In Spanning Tree Protocol operations, the root bridge election is determined by the lowest Bridge ID (BID). The BID is calculated using the bridge priority plus the switch MAC address. Because all switches initially share the default priority of

32768

, explicitly lowering the priority value of a switch (for example, to

24576

4096

) ensures it possesses the lowest BID in the network and becomes the root bridge.

Step-by-Step Solution

Analyze how STP selects the root bridge.

STP compares Bridge IDs across all switches in the Layer 2 domain.

The switch with the lowest Bridge ID is elected as the root bridge.

Examine the composition of the Bridge ID.

The Bridge ID consists of a 2-byte Bridge Priority combined with a 6-byte System MAC Address.

Bridge Priority is evaluated first before MAC address tiebreakers.

Determine the necessary configuration change.

Lowering the bridge priority below the default value of 32768 creates a smaller Bridge ID value than all competing switches.

A smaller numerical priority guarantees winning the root bridge election.

Key Concept

STP Root Bridge Election Mechanics

Estimated Time:45s

Question 255Question →

A network engineer is configuring DHCP relay services on a Layer 3 core switch to service a newly created IoT VLAN (VLAN 50, $172.20.50.0/24$ ). Centralized DHCP services reside on server $192.168.10.10/24$ . The engineer creates Switch Virtual Interface (SVI) `Vlan50` with IP address $172.20.50.1/24$ , but accidentally applies the `ip helper-address 192.168.10.10` command to the Layer 3 point-to-point uplink interface ( $172.20.100.2/30$ ) connected to the datacenter router instead of SVI `Vlan50`. Packet captures confirm client devices on VLAN 50 are sending DHCP DISCOVER broadcast frames, yet no relay traffic reaches the DHCP server. Which of the following best explains why the DHCP relay process fails?

The DHCP relay agent intercepts broadcasts only on the interface where the helper address is configured; applying it to the uplink interface prevents the switch from intercepting and relaying DISCOVER broadcasts arriving on the client SVI.

The relay agent successfully forwards DISCOVER packets out the uplink interface using the uplink IP address (

172.20.100.2

) as the gateway IP (

giaddr

), causing the server to fail because no scope exists for the uplink subnet.

The relay helper service encapsulates DISCOVER traffic into TCP port 67 packets by default, causing the central firewall to drop the traffic because DHCP servers respond exclusively to UDP port 68.

The relay agent converts incoming unicast DISCOVER requests into Layer 2 broadcasts across VLAN 50, but because the uplink interface resides in a separate broadcast domain, Layer 3 switches drop the frames.

Show answer & explanation

Answer: The DHCP relay agent intercepts broadcasts only on the interface where the helper address is configured; applying it to the uplink interface prevents the switch from intercepting and relaying DISCOVER broadcasts arriving on the client SVI.

Answer

A DHCP relay agent (such as Cisco's `ip helper-address`) must be enabled on the specific ingress interface (e.g., SVI or subinterface) facing the client subnets. When client devices broadcast DHCP DISCOVER messages (`255.255.255.255`), the Layer 3 device inspects the ingress interface. If no relay service is enabled on that specific interface, the broadcast is dropped at the Layer 3 boundary. Applying the helper command to an outbound uplink interface only instructs the switch to listen for broadcasts arriving on that uplink, failing to capture or relay any client traffic originating on VLAN 50.

Step-by-Step Solution

Analyze client frame transmission on VLAN 50

Workstations broadcast DHCP DISCOVER frames (

255.255.255.255

) at Layer 2/3 onto SVI `Vlan50` (

172.20.50.1

Unconfigured hosts do not possess an IP address and must broadcast locally to locate a DHCP server.

Evaluate Layer 3 boundary interface configuration

SVI `Vlan50` lacks an active `ip helper-address` statement. The Layer 3 engine drops the broadcast packet at the boundary.

Routers and Layer 3 switches discard Layer 2/3 broadcasts by default unless an active relay agent daemon is configured on that specific ingress interface.

Assess uplink interface configuration

The `ip helper-address` statement placed on the point-to-point uplink interface (

172.20.100.2

) listens only for broadcasts arriving on that specific uplink link.

DHCP relay statements inspect incoming traffic per interface. A helper address on an outbound uplink does not retroactively capture traffic entering through other SVIs.

Key Concept

DHCP Relay Agent Interface Placement and Broadcast Handling

Estimated Time:2m 0s

Question 256Question →

A network administrator is documenting Layer 2 switch interface behaviors and VLAN features for an enterprise network deployment. Match each switching concept on the left with its correct operational description on the right.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Voice VLAN matches with configuring an auxiliary VLAN path with QoS markings; Access Port matches with transmitting traffic for a single assigned VLAN without 802.1Q headers; Trunk Port matches with multiplexing traffic from multiple VLANs using 802.1Q tagging; Broadcast Storm Control matches with dropping excessive Layer 2 broadcast frames exceeding defined thresholds.

Each feature corresponds strictly to its operational role: Voice VLAN provides dedicated bandwidth and QoS prioritization for VoIP telephony; Access Port connects host endpoints inside a single untagged VLAN; Trunk Port multiplexes multi-VLAN frames across switches using 802.1Q header encapsulation; Broadcast Storm Control enforces bandwidth caps on broadcast traffic to prevent network disruption.

Step-by-Step Solution

Identify the primary purpose of Voice VLAN technology on enterprise access switches.

Voice VLAN delivers a secondary VLAN tag on a single port for IP phone traffic and applies Quality of Service (QoS) markings.

This separates voice traffic from workstation data traffic while maintaining call quality.

Differentiate between Access Port and Trunk Port forwarding behaviors.

Access ports process untagged frames for a single broadcast domain, whereas trunk ports aggregate multi-VLAN traffic across inter-switch links via 802.1Q headers.

End-user workstations require untagged access ports, while switch-to-switch links require trunks.

Determine the functional role of Broadcast Storm Control.

Storm control monitors ingress traffic levels and discards frames when broadcast, multicast, or unknown unicast traffic exceeds configured limits.

This mitigates Layer 2 loops or rogue device traffic from overwhelming switch CPU and link bandwidth.

Key Concept

Switch Port Modes, VLAN Allocation, and Traffic Control Features

Estimated Time:1m 30s

Question 257Question →

A logistics company operates four separate fulfillment centers located within a 30-mile radius across the same city. The network engineering team connects these facilities using leased dark fiber provided by a municipal telecommunications provider to enable high-speed inter-building communication across the city. Which of the following network types best classifies this deployment?

Metropolitan Area Network (MAN)

Campus Area Network (CAN)

Storage Area Network (SAN)

Personal Area Network (PAN)

Show answer & explanation

Answer: Metropolitan Area Network (MAN)

Answer

Metropolitan Area Network (MAN)

A Metropolitan Area Network (MAN) is designed to connect facilities distributed across a city or metropolitan region (typically covering tens of miles). It relies on municipal or telecommunications provider links such as leased dark fiber.

Step-by-Step Solution

Analyze the geographic scope of the scenario

The network spans multiple facilities across a 30-mile radius within a single city.

Geographic footprint dictates the primary network type classification (PAN, LAN, CAN, MAN, WAN).

Evaluate the underlying connection infrastructure

Leased municipal dark fiber from a local telecommunications provider is utilized.

Networks spanning an entire city using city-wide service provider or municipal infrastructure are classified as Metropolitan Area Networks.

Match the scope and infrastructure to the correct network classification

A city-wide network larger than a CAN (campus) but smaller than a country-wide WAN is a MAN.

A Metropolitan Area Network specifically covers a city or town-sized geographical region.

Key Concept

Geographic Network Classifications (MAN vs CAN vs SAN vs PAN)

Estimated Time:1m 0s

Question 258Question →

A network administrator is managing a border router connected to a single public IP address. The router is currently configured with Port Address Translation (PAT) to allow 200 internal workstations on the private network to access the internet simultaneously. The organization installs a new internal web server at IP address $10.0.5.25$ that must be publicly accessible from the internet on standard HTTP TCP port 80. Remote external users report that connections to the web server time out, while internal workstations continue to access external websites without issue. Which network address translation configuration should the administrator implement on the router to enable inbound access to the web server without disrupting existing outbound client traffic?

Static NAT (Port Forwarding) mapping incoming traffic on public TCP port 80 to internal IP address 10.0.5.25

Dynamic NAT configured with a translation pool consisting of the router's single public IP address

Reconfiguring PAT to route incoming Layer 2 frame headers directly to the internal server's MAC address

Changing the web server transport protocol to UDP port 80 to permit bi-directional PAT session traversal

Show answer & explanation

Answer: Static NAT (Port Forwarding) mapping incoming traffic on public TCP port 80 to internal IP address 10.0.5.25

Answer

Static NAT (Port Forwarding) mapping incoming traffic on public TCP port 80 to internal IP address 10.0.5.25

Static NAT (or Port Forwarding) establishes a persistent translation rule mapping incoming traffic on a specific public IP and port (TCP 80) to the private IP address of the internal web server (

10.0.5.25

). This enables external clients to reach the web server while preserving the existing PAT configuration for outbound internal traffic.

Step-by-Step Solution

Analyze the technical requirements and existing configuration

Outbound hosts share one public IP address via PAT (many-to-one translation). The internal web server requires a static inbound translation rule on a specific port.

PAT dynamically maps ephemeral source ports for outbound connections but does not open persistent inbound listening ports for external requests.

Evaluate NAT types for inbound service publishing

Static NAT (specifically static PAT or port forwarding) explicitly routes external packets arriving on public TCP port 80 to private IP address

10.0.5.25

Port forwarding allows a single public IP address to simultaneously host internal server services and process outbound PAT traffic.

Key Concept

Static NAT and Port Forwarding for Inbound Service Accessibility

Question 259Question →

A network host receives an incoming Ethernet frame containing an IP packet directed to a local service. Which TWO of the following actions correctly describe the de-encapsulation steps performed as data moves up the destination protocol stack?

Select all that apply

The Network Interface Card verifies frame integrity using the Frame Check Sequence trailer and strips the Layer 2 header and trailer before passing the payload to the Network layer.

The Network layer examines the Protocol field in the IP header to identify the appropriate Layer 4 protocol to receive the decapsulated payload.

The Data Link layer reads the Layer 4 destination port number to determine which VLAN interface should process the incoming frame payload.

The Network layer checks the destination port number to route the packet payload directly to the correct listening application service.

Show answer & explanation

Answer: The Network Interface Card verifies frame integrity using the Frame Check Sequence trailer and strips the Layer 2 header and trailer before passing the payload to the Network layer.; The Network layer examines the Protocol field in the IP header to identify the appropriate Layer 4 protocol to receive the decapsulated payload.

Answer

The Network Interface Card verifies frame integrity using the Frame Check Sequence trailer and strips the Layer 2 header and trailer before passing the payload to the Network layer, and the Network layer examines the Protocol field in the IP header to identify the appropriate Layer 4 protocol to receive the decapsulated payload.

During de-encapsulation, each layer inspects and removes its corresponding header or trailer before passing the remaining payload to the layer above. At Layer 2, frame integrity is verified using the Frame Check Sequence (FCS), after which the Layer 2 header and trailer are removed. At Layer 3, the Network layer inspects the Protocol field within the IP header to determine which Transport layer protocol (such as TCP or UDP) receives the payload.

Step-by-Step Solution

Analyze Layer 2 frame processing and de-encapsulation

The host physical interface receives incoming signals, builds the frame, verifies checksum integrity using the Frame Check Sequence (FCS) in the trailer, and strips the Ethernet header and trailer.

De-encapsulation progresses from lower layers to higher layers, with each layer removing its respective control headers and trailers.

Analyze Layer 3 header evaluation and protocol demultiplexing

The Network layer receives the IP packet, verifies target logical addressing, and inspects the IP header Protocol field to pass the payload to the appropriate Layer 4 handler (such as TCP or UDP).

The Protocol field in the IP header specifies the upper-layer protocol driver that must process the enclosed payload.

Key Concept

De-encapsulation protocol stack unwrapping and header field demultiplexing

Estimated Time:1m 30s

Question 260Question →

A network engineer is troubleshooting IP address acquisition issues for client hosts residing on VLAN 50 ( $172.16.50.0/24$ ). The centralized DHCP server ( $10.10.10.5$ ) is active and reachable via ping from the core router. Packet captures indicate that client $DHCPDISCOVER$ broadcast packets are successfully arriving at the switch Virtual Interface (SVI 50), but the Layer 3 switch fails to generate and forward unicast DHCP messages to the remote DHCP server. Which of the following configuration issues on the Layer 3 switch explains why the DHCP relay agent is unable to forward the client requests?

The switch interface SVI 50 lacks an assigned IPv4 address, preventing the relay agent from populating the gateway IP address (

giaddr

) field required for forwarding.

The ip helper-address command was incorrectly configured on the switch interface connected to the DHCP server instead of the client-facing SVI 50 interface.

The relay agent attempted to establish a TCP session on port 67 to forward the request, which was dropped by the DHCP server.

The relay agent attempted to intercept client traffic on UDP port 67 instead of listening on UDP port 68.

Show answer & explanation

Answer: The switch interface SVI 50 lacks an assigned IPv4 address, preventing the relay agent from populating the gateway IP address ( $giaddr$ ) field required for forwarding.

Answer

The switch interface SVI 50 lacks an assigned IPv4 address, preventing the relay agent from populating the gateway IP address (

giaddr

) field required for forwarding.

For a DHCP relay agent to successfully forward a client's broadcast request as a unicast packet, the receiving Layer 3 interface (SVI 50) must have a valid IP address. The relay agent writes this IP address into the gateway IP address (

giaddr

) field of the DHCP header. The remote DHCP server relies on the

giaddr

value to determine which IP address scope to allocate from. If no IP address is assigned to the SVI, the packet cannot be populated with a valid

giaddr

and is dropped by the relay agent.

Step-by-Step Solution

Analyze the role of the DHCP relay agent (IP Helper) on a Layer 3 interface.

Identified that when a Layer 3 interface intercepts a DHCP broadcast (

DHCPDISCOVER

), it encapsulates the request into a unicast IPv4 packet targeted at the configured DHCP server IP.

Broadcast frames cannot traverse Layer 3 subnet boundaries natively.

Examine how the central DHCP server identifies which scope/pool to assign.

The relay agent inserts its own interface IPv4 address into the Gateway IP Address (

giaddr

) field of the DHCP message header.

Without a valid

giaddr

, the centralized DHCP server has no way of knowing which subnet pool the client belongs to.

Correlate the failure symptom with interface configuration prerequisites.

If SVI 50 does not have an IP address assigned, the relay agent cannot populate

giaddr

and will drop the forwarding operation entirely.

An unnumbered or unconfigured L3 interface lacks the local network IP identity needed for DHCP relay processing.

Key Concept

DHCP Relay Agent and GIADDR Population

Estimated Time:2m 0s

PreviousPage 13 / 112Next

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