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Question 161Question →

An enterprise workstation attempts to connect to an external service by domain name (web.example.com) for the first time. Arrange the following DNS lookup and name resolution steps in the correct sequential order from the client's initial request to receiving the final IP address.

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Answer

The correct chronological sequence is: local cache/hosts file check, recursive query to configured enterprise DNS resolver over UDP port 53, iterative query to Root Name Server, iterative query to TLD Name Server, and finally iterative query to Authoritative Name Server for the host IP mapping.
DNS resolution begins locally on the host by evaluating local memory cache and hosts file entries. If unmapped, the host issues a recursive request over UDP port 53 to its configured enterprise DNS resolver. The resolver then carries out iterative queries starting at the Root level, proceeding to the TLD server level, and finally reaching the Authoritative server that returns the definitive resource record mapping.

Step-by-Step Solution

1
Evaluate local host cache
Workstation verifies if web.example.com exists in local resolver cache or local hosts file.
Checking local host cache avoids unnecessary network traffic and speeds up resolution.
2
Issue client recursive query
Workstation sends a DNS query to the designated local DNS server asking it to complete the full lookup.
Clients use recursive queries so the local DNS server takes responsibility for traversing the DNS hierarchy.
3
Query Root server
Enterprise DNS server contacts a Root Name Server.
Root servers provide referrals to the Top-Level Domain (TLD) servers responsible for extensions such as .com.
4
Query TLD server
Enterprise DNS server queries the TLD server for .com.
TLD servers store information pointing to the specific domain's authoritative name servers.
5
Query Authoritative server
Enterprise DNS server queries the Authoritative server for example.com and gets the host IP address (A record).
Authoritative servers contain the actual DNS resource records for hosts in their managed domain zone.

Key Concept

DNS Name Resolution Mechanics and Server Roles
Question 162Question →

An network engineer is analyzing how OSPFv2 resolves Designated Router (DR) selection on a multiaccess Ethernet segment when multiple candidate routers initialize simultaneously. Arrange the tie-breaking criteria in order of evaluation precedence, starting with the primary criterion evaluated first (highest precedence) at the top down to the final fallback tie-breaker at the bottom.

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Answer

The correct evaluation sequence for OSPF DR selection precedence is: 1. Highest OSPF interface priority value (1–255), 2. Explicitly configured OSPF router ID (`router-id` command), 3. Highest IP address among active loopback interfaces, and 4. Highest IP address among active physical interfaces.
During an OSPF DR/BDR election on a broadcast multiaccess segment, routers first compare interface priority values (1 to 255). If priorities are tied, the election uses the OSPF Router ID as the tie-breaker. The Router ID selection hierarchy itself evaluates an explicitly configured router ID first, followed by the highest active loopback IP address, and finally the highest active physical interface IP address.

Step-by-Step Solution

1
Identify the primary parameter evaluated during OSPF DR/BDR elections on multiaccess networks.
OSPF interface priority is evaluated first. Priority values range from 0 to 255, where priority 0 disables election participation and higher values win.
Interface priority explicitly allows network administrators to control DR/BDR roles regardless of IP addressing.
2
Determine the highest precedence method for tie-breaking using the OSPF Router ID when interface priorities match.
An explicitly configured `router-id` under the OSPF router process is evaluated first.
Manual CLI configuration overrides all dynamic IP address collection logic.
3
Identify the dynamic fallback method for Router ID derivation when no manual Router ID is set.
The highest IPv4 address on any active (up/up) loopback interface is chosen.
Loopback interfaces are preferred over physical interfaces due to their logical stability.
4
Identify the final fallback method for Router ID derivation.
The highest IPv4 address on any active (up/up) physical interface is chosen.
Physical interface IP addresses serve as the last-resort tie-breaker when no explicit router ID or loopbacks are present.

Key Concept

OSPF DR/BDR election logic prioritizes interface priority first, using Router ID (derived via explicit CLI > highest loopback IP > highest physical IP) as a sequential tie-breaker.
Question 163Question →

When a Cisco router receives an IPv4 unicast packet and must select the single best route for forwarding from multiple potential routing table candidates, in what sequence does the router apply its decision logic? Place the steps in the correct order from first to last.

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Answer

The correct order of router decision logic is: 1) Inspect the packet header to extract the destination IPv4 address, 2) Filter candidate routes using Longest Prefix Match (most specific subnet mask length), 3) Compare Administrative Distance (AD) to select the most believable routing source among identical prefix length matches, 4) Compare routing protocol metrics to choose the lowest cost path among identical prefix matches from the same protocol, and 5) Determine the next-hop IPv4 address and associated outbound interface from the selected best route entry.
Router forwarding decision logic follows a strict order of operations: First, the destination IPv4 address is read from the packet header. Second, the router searches its routing table for candidate routes and selects the longest prefix match (most specific mask). Third, if multiple routes have identical subnet mask lengths from different routing sources, Administrative Distance (AD) is evaluated to pick the lowest AD source. Fourth, if identical prefix routes come from the same routing source, the metric is evaluated to select the lowest cost path. Finally, the next-hop IP and egress interface are resolved for forwarding.

Step-by-Step Solution

1
Identify initial packet processing.
Destination IPv4 address is extracted from the IPv4 header.
The router needs the target IP address before searching the routing table.
2
Apply Longest Prefix Match (LPM).
Candidate routes are evaluated strictly by prefix length (number of matching subnet mask bits).
LPM is the primary criterion in IPv4 forwarding. AD and metric are ignored until LPM narrows candidates to identical prefix lengths.
3
Evaluate Administrative Distance (AD).
If a tie exists in prefix length between different routing sources, the route with the lowest AD is selected.
AD measures route believability/trustworthiness across different routing sources.
4
Evaluate protocol metric.
If candidate routes have identical prefix lengths and originate from the same routing protocol, the path with the lowest metric is chosen.
Metric measures the internal path cost for a specific routing protocol.
5
Extract forwarding parameters.
The router obtains the egress interface and next-hop IP address for packet encapsulation.
This information is needed to build the new Layer 2 frame and transmit the packet.

Key Concept

Router Forwarding Decision Hierarchy (LPM -> AD -> Metric -> Next-Hop Extraction)
Estimated Time:1m 30s
Question 164Question →

A network administrator needs to create VLAN 35 named SALES on a Cisco Catalyst switch and assign interface FastEthernet0/5 as a static access port in this VLAN, starting from Privileged EXEC mode (`Switch#`). Place the following Cisco IOS CLI commands in the correct sequential order from first to last.

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Answer

The correct command sequence begins with entering global configuration mode using `configure terminal`, creating VLAN 35 using `vlan 35`, setting the VLAN name with `name SALES`, entering the interface context via `interface FastEthernet0/5`, configuring the interface operating mode using `switchport mode access`, and finally assigning the interface to the VLAN using `switchport access vlan 35`.
In Cisco IOS, configuration follows a strict hierarchy. From Privileged EXEC mode (`Switch#`), global configuration mode must first be accessed via `configure terminal`. Once in global configuration mode, `vlan 35` creates the VLAN and shifts context to VLAN sub-mode (`config-vlan`), where `name SALES` sets the VLAN name. The administrator then navigates directly to interface configuration mode using `interface FastEthernet0/5`. Within interface configuration mode (`config-if`), the port mode is explicitly configured using `switchport mode access`, followed by assigning the port to VLAN 35 with `switchport access vlan 35`.

Step-by-Step Solution

1
Enter Global Configuration Mode
Prompt changes from `Switch#` to `Switch(config)#`.
Global configuration commands like VLAN creation and interface navigation can only be initiated from global configuration mode.
2
Create VLAN 35
Prompt changes from `Switch(config)#` to `Switch(config-vlan)#`.
Issuing `vlan 35` creates the Layer 2 broadcast domain in the VLAN database and opens VLAN configuration mode.
3
Assign VLAN Name
VLAN 35 is assigned the name SALES in the switch database.
The `name` command must be run while in VLAN configuration mode.
4
Navigate to Interface FastEthernet0/5 Context
Prompt changes to `Switch(config-if)#`.
Interface parameters can only be altered when inside the specific interface configuration sub-mode.
5
Set Port Operational Mode to Access
Dynamic Trunking Protocol (DTP) negotiation is disabled or restricted, locking the port to non-trunking access mode.
Executing `switchport mode access` explicitly sets the interface into access mode before or during VLAN membership assignment.
6
Associate Interface with VLAN 35
Traffic untagged on FastEthernet0/5 is assigned to VLAN 35.
The command `switchport access vlan 35` binds the interface to the specified access VLAN.

Key Concept

Cisco IOS CLI command hierarchy for VLAN creation and static access port configuration
Question 165Question →

A non-root switch running Rapid PVST+ receives BPDUs on multiple interfaces with identical path costs to the Root Bridge. Place the tie-breaker criteria in the correct sequential order (from first evaluated to last evaluated) that the switch uses to select its Root Port.

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Answer

The correct order of evaluation for selecting a Root Port in Rapid PVST+ is: 1) Lowest cumulative root path cost, 2) Lowest sender Bridge ID (BID), 3) Lowest sender port priority, and 4) Lowest sender port number.
When a non-root switch running Rapid PVST+ must select a Root Port from multiple candidate interfaces, it follows a strict four-step tie-breaker sequence: first, it checks for the lowest cumulative root path cost; second, the lowest sender Bridge ID (BID); third, the lowest sender port priority; and fourth, the lowest sender port number (interface ID).

Step-by-Step Solution

1
Evaluate Root Path Cost
The switch identifies paths with the lowest total cost to reach the Root Bridge.
STP primary objective is forwarding traffic over the shortest cost path.
2
Evaluate Sender Bridge ID
If path costs are equal across multiple candidate ports, compare neighboring switches' BIDs.
Breaks ties when multiple neighboring switches offer equal-cost paths.
3
Evaluate Sender Port Priority
If connected to the same neighbor over multiple links, compare the neighbor's port priority values.
Differentiates multiple links arriving from a single neighboring switch.
4
Evaluate Sender Port Number
If sender port priority values are identical (default 128), select the port connected to the lower sender port number.
Provides a definitive final tie-breaker for parallel connections.

Key Concept

Rapid PVST+ Root Port Selection Tie-Breaker Sequence
Question 166Question →

A network engineer is configuring a new Cisco IOS router (R1) to synchronize its system time with a primary enterprise NTP server operating at Stratum 2. R1 is also expected to act as an NTP server for downstream switches once synchronized. Arrange the operational steps in the exact chronological sequence in which R1 processes NTP synchronization from initial CLI configuration to serving downstream clients.

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Answer

The correct sequence starts with entering the NTP server configuration command, followed by sending UDP port 123 query packets, receiving the Stratum 2 response, calculating the local Stratum 3 value, and finally transitioning to synchronized state while serving downstream clients.
The operational sequence moves logically from CLI command execution, outward network request over UDP 123, inbound response processing, mathematical stratum calculation (2+1=32 + 1 = 3), to local state synchronization and downstream service activation.

Step-by-Step Solution

1
Identify the initial configuration trigger
Execution of 'ntp server 10.10.10.1' initializes the local NTP daemon polling timer.
NTP operations cannot begin until a server association is defined in configuration.
2
Determine initial packet transmission details
R1 sends outgoing NTP client polling messages using UDP port 123.
NTP uses UDP port 123 for all client/server communications.
3
Process server response details
R1 receives packet payload containing Stratum 2 marker from 10.10.10.1.
The upstream server reports its own stratum distance from reference clock (Stratum 2).
4
Perform Stratum level mathematical calculation
Local stratum is evaluated as Server Stratum+1=2+1=3\text{Server Stratum} + 1 = 2 + 1 = 3.
Every network hop down the NTP hierarchy increments the Stratum level by exactly 1.
5
Establish synchronized state and downstream server role
System clock updates to synchronized state, enabling R1 to answer downstream queries at Stratum 3.
A Cisco router will not serve authoritative time to downstream clients until its own clock is synchronized to an upstream source.

Key Concept

NTP Client-Server Synchronization Workflow and Stratum Calculation
Estimated Time:2m 0s
Question 167Question →

An enterprise router R1 is configured as the active HSRPv1 router for Group 10 with an initial priority of 110 and preemption enabled. R1 tracks its WAN uplink interface GigabitEthernet0/1 with a priority decrement value of 20. Router R2 is configured as the standby router for Group 10 with a priority of 100 and preemption enabled. Place the operational events in the exact chronological sequence following a line-protocol failure on R1's GigabitEthernet0/1 interface until failover convergence completes.

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Answer

The correct chronological sequence is: (1) R1 detects tracked interface failure -> (2) R1 decrements priority to 90 -> (3) R1 sends Hello with priority 90 -> (4) R2 compares priorities (100 vs 90) -> (5) R2 transmits an HSRP Coup message -> (6) R2 enters Active state and issues a Gratuitous ARP while R1 becomes Standby.
HSRP convergence follows a strict sequence when interface tracking degrades priority: detection of interface failure occurs first, leading to immediate priority calculation on the active router. The reduced priority is then advertised to the standby router via standard Hello messages. The standby router evaluates the lower priority, triggers preemption by sending a Coup message, assumes the Active state, and finally sends a Gratuitous ARP to re-align Layer 2 switch forwarding tables.

Step-by-Step Solution

1
Detect Link Failure
R1 detects line-protocol failure on GigabitEthernet0/1.
Interface tracking monitors the operational state of the configured interface.
2
Calculate Priority Decrement
R1's priority changes from 110 to 90.
The configured track action automatically subtracts 20 from R1's active priority (110−20=90110 - 20 = 90).
3
Advertise New Priority
R1 sends an HSRP Hello packet containing priority 90.
HSRP routers communicate state changes via periodic Hello messages sent to 224.0.0.2.
4
Evaluate Preemption Criteria
R2 identifies that its priority (100) exceeds R1's reported priority (90).
With preemption configured, a standby router constantly compares received active priority against its own.
5
Signal Takeover
R2 sends an HSRP Coup message.
The Coup message informs the current active router that a higher-priority router is asserting control.
6
Final Convergence & Traffic Steering
R2 transitions to Active, issues a Gratuitous ARP for the virtual IP/MAC, and R1 steps down to Standby.
The Gratuitous ARP updates Layer 2 switch forwarding tables so host traffic is immediately steered to R2.

Key Concept

HSRP Interface Tracking and Preemption Mechanism
Question 168Question →

An enterprise client host without a cached DNS entry needs to connect to an external server using its domain name. Place the steps of the full name resolution flow in the correct chronological order, starting from the client's initial lookup request to the final response delivery.

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Answer

The correct chronological sequence begins with the client host issuing a recursive query to the internal DNS server after checking its local cache. Next, the internal DNS server executes iterative lookups starting at a root DNS server, followed by the TLD DNS server, and finally the domain's authoritative DNS server. Upon receiving the A/AAAA record from the authoritative server, the internal DNS server caches the result and delivers the IP address to the requesting client.
The correct order follows the standard hierarchy of enterprise DNS name resolution. First, the client checks its local cache and queries its local DNS server recursively. Second, if un-cached, the internal recursive DNS server initiates iterative lookups starting at the root servers. Third, the root server redirects the query to the TLD server. Fourth, the TLD server refers the query to the authoritative name server. Fifth, the authoritative name server provides the IP mapping, which the internal server caches before replying to the client host.

Step-by-Step Solution

1
Evaluate host-level resolution steps
Client host checks local cache/hosts file, then sends a recursive lookup request to the configured internal DNS server.
Hosts must exhaust local name resolution mechanisms before querying network resolvers over port 53.
2
Trace top-of-hierarchy DNS server lookup
Internal recursive server queries a Root name server and receives a referral to the TLD name servers.
Iterative resolution moves top-down through the domain namespace starting at the root (".").
3
Trace mid-hierarchy DNS server lookup
Internal recursive server queries the TLD server (such as .com) and receives a referral to the authoritative name server.
TLD servers delegate authority for specific subdomains to organizational name servers.
4
Trace authoritative response acquisition
Internal recursive server queries the domain's authoritative name server and receives the final mapping.
Only the authoritative DNS server for a domain holds the definitive zone file records.
5
Complete recursive loop to client
Internal recursive server caches the mapping according to TTL and returns the resolved address to the client.
The client receives a single final response to satisfy its initial recursive query.

Key Concept

DNS Resolution Hierarchy and Iterative vs Recursive Query Roles
Question 169Question →

A network administrator is connecting a Cisco Catalyst 9800 Series Wireless LAN Controller to an upstream Cisco Catalyst switch using link aggregation (LAG) with LACP. In what logical order should the administrator execute the steps on the Catalyst switch to provision the EtherChannel interface and physical member ports?

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Answer

The correct sequence begins with creating the logical port-channel interface on the switch, applying trunking and VLAN parameters to that logical interface, selecting the physical member interfaces, adding the physical interfaces to the EtherChannel using active LACP mode, and finally verifying bundle operation with the 'show etherchannel summary' command.
To establish link aggregation between a Cisco Catalyst switch and a Cisco Wireless LAN Controller using LACP, standard configuration methodology requires initializing the logical port-channel interface first. Trunking settings (such as switchport mode trunk and VLAN assignments) are defined on the logical port-channel. Next, the target physical member interfaces are selected and bound to the channel group using active LACP mode. Finally, running operational verification commands confirms proper link aggregation state.

Step-by-Step Solution

1
Create the virtual port-channel interface
The logical interface Port-channel 1 is initialized.
Creating the logical interface first provides the administrative entity where trunking parameters will be defined.
2
Configure trunking properties on the port-channel
The port-channel interface is set to switchport mode trunk with explicit native and allowed VLAN parameters.
Defining trunk settings directly on the port-channel interface guarantees uniform configuration for all associated physical ports.
3
Select physical switch interfaces
The physical ports connected to the wireless controller are selected via interface range configuration mode.
Grouping physical interfaces prepares them for enrollment into the EtherChannel bundle.
4
Bind physical ports to the channel group using LACP
The command 'channel-group 1 mode active' enables dynamic LACP negotiation on the physical ports.
LACP active mode allows the switch to initiate negotiation with the Wireless LAN Controller.
5
Verify EtherChannel operation
Output displays flag 'SU' for the port-channel and flag 'P' for each active member port.
Verifying status confirms that LACP negotiation succeeded and traffic can be forwarded across the aggregated links.

Key Concept

Cisco switch EtherChannel and LACP configuration for WLC trunking
Question 170Question →

An enterprise host needs to resolve the IP address of an internal web application server (app.corp.local) after the local cache has expired. Place the steps of the name resolution process in the correct chronological order from first to last.

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Answer

The correct sequence of DNS name resolution steps is: 1) The host checks its local OS DNS client resolver cache and local hosts file. 2) The host encapsulates a recursive DNS query in a UDP datagram with destination port 53 and sends it to its primary configured DNS server. 3) The enterprise DNS server receives the query and checks its authoritative DNS zones. 4) The DNS server formulates an authoritative response packet containing the requested A record. 5) The host receives the DNS response packet and stores the IP address mapping in its local DNS resolver cache.
The correct order follows the standard host-to-server DNS name resolution flow: first, local host resources (cache and hosts file) are inspected. If unresolved, the client sends a recursive UDP query (destination port 53) to its configured local DNS server. The DNS server processes the query against its zone database, generates an authoritative response containing the A record, and returns it to the host. Finally, the host receives the response and caches the IP address locally.

Step-by-Step Solution

1
Evaluate local host resolution mechanisms.
Local resolver cache and hosts file are queried first prior to generating outbound network requests.
Checking local host memory avoids unnecessary network traffic and reduces latency.
2
Transmit DNS request over the local network connection.
A UDP datagram targeted to destination port 53 is forwarded to the designated local DNS server.
Standard DNS queries use UDP port 53 for low-overhead client-to-server communications.
3
Process query at the targeted enterprise DNS server.
The server checks its local authoritative zone files for matching domain records.
Because the domain is internal (corp.local), the internal DNS server acts as the authoritative source.
4
Build DNS server response payload.
An authoritative DNS answer payload containing the IPv4 (A) record is created.
The server must supply the mapped IP address back to the requesting client.
5
Process response on the requesting client host.
The client receives the response and caches the entry according to the record's Time-to-Live (TTL).
Caching allows subsequent applications on the host to reuse the resolved IP address without repeating the DNS lookup.

Key Concept

Client DNS resolution sequence and DNS server roles
Question 171Question →

An enterprise client workstation attempts to access an external web application at `app.partner.example.net` for the first time. Arrange the steps of the complete DNS resolution process in the correct chronological order, starting from the client's initial lookup request to the final IP address retrieval.

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Answer

The correct sequence begins with the client host checking its local resolver cache and hosts file, followed by sending a recursive query to the local internal DNS resolver. The internal resolver then performs iterative queries starting at the root server, proceeding to the .net TLD server, and finally querying the authoritative server for partner.example.net before caching the record and returning the resolved IP address to the client.
The proper sequence follows standard operating system and DNS protocol operational order: local client cache and hosts file check -> client recursive query to the local internal DNS resolver -> internal resolver iterative query to the root name server -> root referral to the TLD server -> TLD referral to the domain authoritative server -> authoritative answer returned, cached by the internal resolver, and forwarded to the client.

Step-by-Step Solution

1
Check local OS resolution mechanisms.
The host OS scans the local `hosts` file and client DNS cache for `app.partner.example.net`.
Local lookup prevents unnecessary network overhead if the IP address is already known locally.
2
Transmit recursive query from client host to configured DNS server.
A UDP port 53 recursive query is sent to the internal enterprise DNS resolver.
The client delegates name resolution responsibility entirely to its configured local DNS server.
3
Initiate iterative resolution from the DNS root hierarchy.
The internal DNS server queries a DNS root hint server (`.`).
When resolving an un-cached external FQDN, the recursive resolver starts lookups at the root zone.
4
Process root referral response.
The root server responds with NS and glue A records for the `.net` TLD servers.
Root servers maintain delegation points for top-level domains.
5
Query TLD name server for domain authority.
The `.net` TLD server provides NS records pointing to authoritative servers for `partner.example.net`.
TLD servers maintain delegations for secondary registered domains under their top-level domain.
6
Fetch definitive record from authoritative server and respond to client.
The authoritative server responds with the `A` record, which the internal server caches and forwards to the requesting client.
Only authoritative name servers hold the master resource records for the targeted domain.

Key Concept

DNS Lookup and Name Resolution Roles in Enterprise Networks
Estimated Time:2m 0s
Question 172Question →

Arrange the Cisco Hot Standby Router Protocol (HSRP) router states in the correct sequential order from initial interface startup to the active forwarding role.

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Answer

The correct sequence of HSRP state transitions from startup to active forwarding is: Initial state, Listen state, Speak state, Standby state, and Active state.
HSRP router state transitions follow a strict logical progression: Initial (startup), Listen (receives Hello packets), Speak (sends Hello packets and joins election), Standby (selected as candidate backup), and Active (forwards virtual IP traffic).

Step-by-Step Solution

1
Identify the initialization state.
The router starts in the Initial state.
An interface must be enabled and initialized before any protocol messages are processed.
2
Determine the discovery phase.
The router transitions to the Listen state.
In the Listen state, the router receives Hello packets from existing group members without sending its own.
3
Identify the election participation phase.
The router moves to the Speak state.
The router sends periodic Hello messages to compete for active or standby router roles.
4
Determine the backup role assignment.
The router enters the Standby state.
The router is designated as the candidate to take over if the active router fails.
5
Identify the primary forwarding role.
The router reaches the Active state.
The elected router actively forwards frames destined to the virtual MAC and virtual IP address.

Key Concept

HSRP Router State Machine Sequence
Question 173Question →

A client workstation is configured to obtain IPv4 addressing dynamically. Arrange the four messages exchanged during the standard DHCP lease process (DORA) in chronological order from first to last.

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Answer

The chronological sequence of the IPv4 DHCP operation is DHCPDISCOVER, DHCPOFFER, DHCPREQUEST, and DHCPACK.
The standard IPv4 DHCP lease negotiation process follows the four-step DORA sequence: Discover (client broadcast), Offer (server response), Request (client selection broadcast), and Acknowledge (server confirmation).

Step-by-Step Solution

1
Identify the initial client discovery broadcast.
DHCPDISCOVER is sent first by the client.
The client has no assigned IP address and must broadcast to discover active DHCP servers.
2
Identify the server offer response.
DHCPOFFER is sent second by the server.
A server receiving the discovery broadcast offers an available IP address and subnet parameters.
3
Identify the client acceptance broadcast.
DHCPREQUEST is sent third by the client.
The client broadcasts its intent to accept the specific offer, allowing unselected servers to release their reserved offers.
4
Identify the server final acknowledgment.
DHCPACK is sent fourth by the server.
The server acknowledges the request and locks in the IP lease parameters for the client.

Key Concept

DHCP DORA Process (Discover, Offer, Request, Acknowledge)
Question 174Question →

A network engineer connects two Cisco Catalyst switches using a point-to-point GigabitEthernet link running Rapid PVST+. Place the steps of the Rapid PVST+ Proposal and Agreement handshaking process in the correct chronological order from first to last.

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Answer

The correct chronological sequence for the Rapid PVST+ Proposal-Agreement handshake is: 1) Upstream switch sends a Proposal BPDU, 2) Downstream switch puts non-edge designated ports into Discarding state (sync), 3) Downstream switch sends an Agreement BPDU, 4) Upstream switch immediately transitions its designated port to Forwarding.
Rapid PVST+ achieves rapid convergence on full-duplex point-to-point links via an explicit handshake. First, an upstream switch sends a Proposal BPDU. Second, the receiving downstream switch performs synchronization by forcing all non-edge designated ports into the Discarding state. Third, the downstream switch returns an Agreement BPDU. Finally, the upstream switch receives the Agreement and immediately transitions its designated port to Forwarding.

Step-by-Step Solution

1
Initiate Handshake
The upstream switch transmits a configuration BPDU with the Proposal bit set on a point-to-point link.
Rapid PVST+ uses explicit handshaking on point-to-point links rather than waiting for 802.1D forward delay timers.
2
Perform Synchronization
The receiving (downstream) switch blocks all non-edge designated ports, putting them into the Discarding state.
Enforcing the synchronization (sync) state isolates the local switch topology to ensure no temporary switching loops are formed.
3
Send Agreement
The downstream switch sends a BPDU back with the Agreement bit set.
This confirms to the upstream neighbor that the downstream switch has isolated its local ports and accepted the proposal.
4
Transition to Forwarding
The upstream switch transitions its designated port directly to the Forwarding state.
Receiving an explicit Agreement allows immediate state transition without waiting for timer expiration.

Key Concept

Rapid PVST+ (802.1w) Proposal-Agreement Synchronization Process
Estimated Time:1m 30s
Question 175Question →

Arrange the following Cisco IOS Syslog severity levels in order from most critical (lowest numeric level) to least critical (highest numeric level).

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Answer

The correct order from most critical to least critical is Emergency (Level 0), Critical (Level 2), Warning (Level 4), and Informational (Level 6).
Cisco IOS Syslog messages follow standard severity levels ranging from 0 (Emergency, highest urgency) to 7 (Debugging, lowest urgency). Sorting from most critical to least critical requires ordering by increasing numeric value: Emergency (0), Critical (2), Warning (4), and Informational (6).

Step-by-Step Solution

1
Identify the numeric severity level assigned to each Syslog level name
Emergency is Level 0, Critical is Level 2, Warning is Level 4, and Informational is Level 6.
Cisco IOS Syslog uses a standard numeric scale from 0 to 7 to define message severity.
2
Sort the identified levels from lowest numeric value to highest numeric value
Emergency (0) -> Critical (2) -> Warning (4) -> Informational (6).
Lower numeric values indicate higher urgency/criticality in Syslog operations.

Key Concept

Syslog Severity Levels (0 to 7)
Estimated Time:1m 0s
Question 176Question →

Place the following Cisco IOS password encryption types in order of security strength, from weakest (least secure) to strongest (most secure).

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Answer

The correct order from weakest to strongest security strength is Type 0 (Plaintext), Type 7 (Reversible Vigenère cipher), Type 5 (MD5 hash), and Type 9 (scrypt hash).
The sequence from weakest to strongest begins with Type 0 (unencrypted plaintext). Next is Type 7, which uses weak, reversible Vigenère encryption intended only to stop casual viewing. Type 5 uses a one-way MD5 hash which cannot be mathematically decrypted. Finally, Type 9 uses the modern memory-hard scrypt algorithm to provide maximum protection against high-speed dictionary and brute-force attacks.

Step-by-Step Solution

1
Identify unencrypted plaintext storage
Type 0 represents completely unencrypted text in the configuration file.
Plaintext offers no protection because anyone viewing the running configuration can read the password.
2
Identify weakly obfuscated passwords
Type 7 is created by 'service password-encryption' using a reversible algorithm.
Type 7 prevents casual shoulder surfing but can be trivially reversed back to plaintext.
3
Identify standard cryptographic hashes
Type 5 relies on the MD5 one-way hash algorithm.
One-way hashes cannot be decrypted back to plaintext, making Type 5 much stronger than Type 7 obfuscation.
4
Identify modern memory-hard password hashes
Type 9 uses the scrypt algorithm for enhanced key derivation.
scrypt is designed to resist hardware-accelerated offline brute-force attacks, making it stronger than MD5.

Key Concept

Cisco IOS Password Encryption Algorithm Types and Relative Security Strengths
Question 177Question →

A network engineer needs to configure link aggregation (LAG) on a Cisco Catalyst switch connected to a Cisco AireOS Wireless LAN Controller (WLC). Arrange the following configuration steps in the correct logical order from first to last to ensure a functional static EtherChannel interface on the switch.

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Answer

The correct order of steps is: 1. Create and enter interface configuration mode for the logical port-channel interface. 2. Configure switchport trunking encapsulation, trunk mode, and allowed VLANs on the port-channel interface. 3. Select the range of physical member interfaces connected to the WLC distribution ports. 4. Bind the physical member interfaces to the port-channel using channel-group mode on.
The correct operational sequence begins by creating the logical port-channel interface and setting its trunking and VLAN parameters. Next, the network engineer selects the physical switch interfaces connected to the controller's distribution ports and assigns them to the channel group using 'mode on'. Static aggregation is required because AireOS WLCs use unnegotiated bundle distribution across all active ports.

Step-by-Step Solution

1
Create the logical port-channel interface on the Catalyst switch.
The port-channel interface (e.g., interface Port-channel 1) is instantiated.
Establishing the logical bundle interface first provides a central point to apply trunking properties.
2
Apply 'switchport mode trunk' and allowed VLAN commands to the port-channel interface.
The logical interface is configured as an 802.1Q trunk carrying required WLAN management and data VLANs.
Applying configurations to the port-channel interface prevents port inconsistency errors across member links.
3
Enter interface range mode for the physical switch ports connecting to the WLC.
Physical ports (e.g., interface range GigabitEthernet1/0/1 - 2) are selected.
Physical interface mode is needed to assign the specific physical links into the aggregated bundle.
4
Issue the 'channel-group 1 mode on' command on the physical interfaces.
Physical interfaces join the port-channel as static EtherChannel members.
Cisco AireOS Wireless LAN Controllers do not negotiate LACP or PAgP control frames; the switch ports must use static channel mode 'on'.

Key Concept

Switch EtherChannel Configuration Sequence for AireOS WLC Link Aggregation
Estimated Time:1m 30s
Question 178Question →

Place the Cisco Hot Standby Router Protocol (HSRP) router states in the correct sequential order from interface initialization to the state where the router assumes primary packet forwarding for the virtual gateway.

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Answer

The correct sequential order of HSRP router states is: Initial State, Listen State, Speak State, Standby State, and Active State.
When HSRP is enabled on an interface, the router progresses systematically through five main states: Initial (interface up), Listen (receives Hello packets to learn virtual IP and detect peers), Speak (transmits periodic Hello packets to enter active/standby election), Standby (elected backup router), and finally Active (elected primary gateway responsible for handling virtual IP traffic).

Step-by-Step Solution

1
Identify the state representing initial interface bring-up
Initial State is the starting point before any HSRP communication begins.
HSRP process initiates when the underlying Layer 3 interface comes up.
2
Identify the state where the router observes existing HSRP peers without transmitting
Listen State follows Initial State.
The router must first hear if active or standby routers already exist on the segment.
3
Determine when the router starts transmitting Hello packets to join the election
Speak State follows Listen State.
The router sends Hello packets to announce its presence and participate in role selection.
4
Identify the interim role prior to becoming the primary forwarder
Standby State follows Speak State.
The router acts as the designated backup router before assuming the active role if election parameters permit.
5
Identify the final operational state responsible for forwarding virtual IP traffic
Active State is the final state.
The elected active router answers ARP requests for the virtual IP and forwards user traffic.

Key Concept

HSRP State Machine Transitions
Question 179Question →

Place the following operational steps in the correct chronological order to show how a Cisco router configured as a DHCP relay agent processes an incoming client discovery message.

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Answer

The correct sequence begins with the host client broadcasting a DHCP DISCOVER packet on its local subnet. Next, the local router interface receives the broadcast packet and evaluates the configured ip helper-address. The router then inserts its local receiving interface IP address into the Gateway IP Address (giaddr) field. Finally, the router converts the packet to a unicast IP packet and forwards it to the target DHCP server address.
When an unconfigured host requests an IP address, it broadcasts a DHCP DISCOVER frame. The local router interface intercepts this broadcast, modifies the DHCP header by adding its receiving interface IP to the giaddr field, and changes the destination from broadcast to unicast directed at the configured DHCP server IP.

Step-by-Step Solution

1
Identify the client-side initiation of the DHCP process.
The host client generates a broadcast DHCP DISCOVER message.
Unconfigured hosts must use broadcast addressing to discover available DHCP servers on the local segment.
2
Determine the initial reception step by the relay agent.
The router interface captures the broadcast and checks for an active ip helper-address statement.
The ip helper-address command instructs the interface to process incoming UDP port 67 broadcast traffic.
3
Identify the mandatory payload modification performed by the relay agent.
The router writes its own interface IP into the packet's giaddr field.
Without the giaddr field populated, the central server cannot determine which pool and subnet address range to offer.
4
Determine the final packet forwarding operation.
The router forwards the modified DHCP request as a unicast packet to the central DHCP server.
Broadcasts are not routed by default; relaying requires converting the frame into a unicast transmission targeting the DHCP server.

Key Concept

DHCP Relay Agent Operation and Payload Modification (giaddr)
Estimated Time:45s
Question 180Question →

A network operations center engineer is reviewing syslog messages emitted by a Cisco IOS router. Arrange the following syslog events in order from HIGHEST severity (lowest numerical severity level) to LOWEST severity (highest numerical severity level).

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Answer

The correct sequence from highest severity (lowest numeric value) to lowest severity (highest numeric value) is: 1) Hardware watchdog system failure (Level 0 - Emergency), 2) Duplex mismatch error (Level 3 - Error), 3) Configuration commit notice (Level 5 - Notice), 4) Syslog server initialization message (Level 6 - Informational), and 5) Debug packet trace output (Level 7 - Debugging).
The correct ordering aligns with the standard Cisco IOS Syslog numerical severity scale: 0 (Emergency), 1 (Alert), 2 (Critical), 3 (Error), 4 (Warning), 5 (Notice), 6 (Informational), and 7 (Debugging). The hardware failure message is Emergency (Level 0), followed by interface error (Level 3), configuration change (Level 5), syslog service initialization (Level 6), and debug packet trace output (Level 7).

Step-by-Step Solution

1
Determine the numerical severity code assigned to each Cisco IOS event category in the Syslog standard.
System failure = Level 0 (Emergency); Duplex mismatch = Level 3 (Error); Configuration commit = Level 5 (Notice); Syslog host initialization = Level 6 (Informational); Debug packet trace = Level 7 (Debugging).
Cisco IOS categorizes log severity from Level 0 (most critical) through Level 7 (least critical).
2
Order the identified events in ascending numerical order of their severity levels.
The numerical order is 0 -> 3 -> 5 -> 6 -> 7.
A lower numerical severity level corresponds to a higher criticality event in Syslog architecture.

Key Concept

Cisco IOS Syslog severity level taxonomy (0-Emergency to 7-Debugging)
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