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Question 910
A campus configures very aggressive BFD intervals on thousands of routed links and then sees intermittent neighbor flaps at peak CPU. Choose THREE statements that form the design action, direct verification, and deployment safeguard. (Choose THREE.)
- Tune BFD intervals and session scale to supported hardware and realistic detection requirements.
- Confirm trunk and relay paths, IP phones, and bindings before enforcing trust boundaries.
- Approved intersite traffic carries the expected segmentation context without undesired leakage.
- Trust only legitimate DHCP server/uplink paths and keep edge client ports untrusted.
- Baseline platform BFD resource consumption and event rates before decreasing timers.
- True failures are found promptly while healthy links no longer reset under ordinary control-plane load.
Explanation
Correct Answers
A:Tune BFD intervals and session scale to supported hardware and realistic detection requirements. This is the corrective design for the stated topology.
E:Baseline platform BFD resource consumption and event rates before decreasing timers. This applies directly to the reported network-design requirement.
F:True failures are found promptly while healthy links no longer reset under ordinary control-plane load. This is the observable acceptance check for the change.
Incorrect Answers
B:This offered choice, “Confirm trunk and relay paths, IP phones, and bindings before enforcing trust boundaries”, addresses a separate concern. This statement relates to a different requirement: A routed campus uses DHCP snooping on access switches but marks every endpoint port trusted for convenience. It does not address the condition described here.
C:This statement relates to a different requirement: An organization needs consistent segmentation across two SD-Access fabric sites connected by a routed MPLS service. It does not address the condition described here.
D:This offered choice, “Trust only legitimate DHCP server/uplink paths and keep edge client ports untrusted”, addresses a separate concern. This statement relates to a different requirement: A routed campus uses DHCP snooping on access switches but marks every endpoint port trusted for convenience. It does not address the condition described here.
Question 911
A regional site uses EIGRP neighbors with mismatched autonomous system numbers despite matching IP subnet and authentication. Select TWO statements that together define the best corrective design and its acceptance evidence. (Choose TWO.)
- Neighbors establish in the planned routing domain and exchange expected route prefixes.
- Evaluate a suitable NAT64/DNS64 or application-proxy boundary with supported protocol assumptions.
- Refine the summary to reflect reachable networks and provide appropriate handling for withdrawn components.
- Align the intended EIGRP AS and verify the relevant interface network and authentication settings.
- The neighbors reach FULL and application packets traverse without fragmentation problems.
Explanation
Correct Answers
A:Neighbors establish in the planned routing domain and exchange expected route prefixes. This is the observable acceptance check for the change.
D:Align the intended EIGRP AS and verify the relevant interface network and authentication settings. This applies directly to the reported network-design requirement.
Incorrect Answers
B:This offered choice, “Evaluate a suitable NAT64/DNS64 or application-proxy boundary with supported protocol assumptions”, addresses a separate concern. That answer belongs to this other scenario: A new IPv6-only client subnet must access a legacy IPv4-only web endpoint through an enterprise gateway. It does not establish the necessary change in this case.
C:That answer belongs to this other scenario: Branches summarize their local EIGRP networks at a hub-facing boundary, but a detached subnet is included in the summary. It does not establish the necessary change in this case.
E:That answer belongs to this other scenario: Two OSPF neighbors on a routed core link are stuck in EXSTART/EXCHANGE and one endpoint uses an incompatible MTU. It does not establish the necessary change in this case.
Question 912
Two independent PIM-SM domains each use local rendezvous points but remote sources must be discovered across the domains. Choose THREE statements that form the design action, direct verification, and deployment safeguard. (Choose THREE.)
- Segment management-plane access by role/tenant and enforce ACLs and authentication at the boundaries.
- Confirm all clients and intermediate devices support the required SSM join model.
- Sources registered in either domain become discoverable to intended remote receivers.
- Assess RP and MSDP scaling and supported migration alternatives before deployment.
- Evaluate supported MSDP-based source active exchange or a modern supported interdomain design.
- Unit administrators can reach authorized nodes but are denied management of unrelated infrastructure.
Explanation
Correct Answers
C:Sources registered in either domain become discoverable to intended remote receivers. This is the observable acceptance check for the change.
D:Assess RP and MSDP scaling and supported migration alternatives before deployment. This applies directly to the reported network-design requirement.
E:Evaluate supported MSDP-based source active exchange or a modern supported interdomain design. This is the corrective design for the stated topology.
Incorrect Answers
A:This offered choice, “Segment management-plane access by role/tenant and enforce ACLs and authentication at the boundaries”, addresses a separate concern. This statement relates to a different requirement: Two business units share one management VLAN with unrestricted access to each other's routers. It does not address the condition described here.
B:This statement relates to a different requirement: A 10,000-receiver IPTV deployment requires one-to-many traffic from known sources but still uses RP discovery for each stream. It does not address the condition described here.
F:This offered choice, “Unit administrators can reach authorized nodes but are denied management of unrelated infrastructure”, addresses a separate concern. This statement relates to a different requirement: Two business units share one management VLAN with unrestricted access to each other's routers. It does not address the condition described here.
Question 913
A customer needs private route separation for 12 branches over a shared provider backbone, not a single Ethernet broadcast domain. Select TWO statements that together define the best corrective design and its acceptance evidence. (Choose TWO.)
- Evaluate an appropriately isolated L2VPN or pseudowire with defined loop, bandwidth and MTU constraints.
- Expected tagged traffic traverses the authorized EVC and unrelated tags are isolated.
- Each branch exchanges only authorized VPN routes while the provider backbone transports traffic without L2 extension.
- Choose a provider MPLS Layer 3 VPN with appropriate VRF route-target isolation and customer-to-provider routing.
- Align the service's supported VLAN encapsulation and mapping with the carrier's EVC definition.
Explanation
Correct Answers
C:Each branch exchanges only authorized VPN routes while the provider backbone transports traffic without L2 extension. This is the observable acceptance check for the change.
D:Choose a provider MPLS Layer 3 VPN with appropriate VRF route-target isolation and customer-to-provider routing. This applies directly to the reported network-design requirement.
Incorrect Answers
A:That answer belongs to this other scenario: Two industrial sites require transparent delivery of a small set of Ethernet services and reject routing between their private LANs. It does not establish the necessary change in this case.
B:This offered choice, “Expected tagged traffic traverses the authorized EVC and unrelated tags are isolated”, addresses a separate concern. That answer belongs to this other scenario: Two enterprise buildings use separate Metro Ethernet UNI ports, yet their operators assume the provider will preserve any configured customer VLAN ID. It does not establish the necessary change in this case.
E:This offered choice, “Align the service's supported VLAN encapsulation and mapping with the carrier's EVC definition”, addresses a separate concern. That answer belongs to this other scenario: Two enterprise buildings use separate Metro Ethernet UNI ports, yet their operators assume the provider will preserve any configured customer VLAN ID. It does not establish the necessary change in this case.
Question 914
A customer rents virtual machines from a provider and must patch their operating systems, but procurement classifies the service as SaaS. Choose THREE statements that form the design action, direct verification, and deployment safeguard. (Choose THREE.)
- Review the contract's actual management boundary rather than the marketing name.
- Evaluate RESTCONF with its YANG-modeled REST resources and authorized HTTP operations.
- Confirm HTTP authentication, model paths, ETags and expected status-code handling.
- The responsibility matrix assigns OS patching and application security to the appropriate customer team.
- An approved RESTCONF PATCH changes only the intended interface fields and a GET verifies effective state.
- Classify the offering as IaaS and document customer responsibilities for guest OS, identities and workloads.
Explanation
Correct Answers
A:Review the contract's actual management boundary rather than the marketing name. This applies directly to the reported network-design requirement.
D:The responsibility matrix assigns OS patching and application security to the appropriate customer team. This is the observable acceptance check for the change.
F:Classify the offering as IaaS and document customer responsibilities for guest OS, identities and workloads. This is the corrective design for the stated topology.
Incorrect Answers
B:This offered choice, “Evaluate RESTCONF with its YANG-modeled REST resources and authorized HTTP operations”, addresses a separate concern. This statement relates to a different requirement: A Python network tool must update structured interface configuration through web-style requests but the engineer chooses CLI scraping instead of a supported API. It does not address the condition described here.
C:This offered choice, “Confirm HTTP authentication, model paths, ETags and expected status-code handling”, addresses a separate concern. This statement relates to a different requirement: A Python network tool must update structured interface configuration through web-style requests but the engineer chooses CLI scraping instead of a supported API. It does not address the condition described here.
E:This offered choice, “An approved RESTCONF PATCH changes only the intended interface fields and a GET verifies effective state”, addresses a separate concern. This statement relates to a different requirement: A Python network tool must update structured interface configuration through web-style requests but the engineer chooses CLI scraping instead of a supported API. It does not address the condition described here.
Question 915
A branch router redistributes a static default to the campus IGP without approval, causing arbitrary sites to shift egress. Select TWO statements that together define the best corrective design and its acceptance evidence. (Choose TWO.)
- Place route summarization at contiguous ownership boundaries and preserve specific exceptions needed for proper egress.
- Explicitly control default route origination and conditional advertisements at authorized borders.
- The corporate campus receives only the approved default from designated egress nodes.
- Place primary and secondary STP root roles at the appropriate distribution devices for the planned VLAN sets.
- Prefix changes within a campus no longer cause unnecessary global churn while remote packets use the proper border.
Explanation
Correct Answers
B:Explicitly control default route origination and conditional advertisements at authorized borders. This applies directly to the reported network-design requirement.
C:The corporate campus receives only the approved default from designated egress nodes. This is the observable acceptance check for the change.
Incorrect Answers
A:This offered choice, “Place route summarization at contiguous ownership boundaries and preserve specific exceptions needed for proper egress”, addresses a separate concern. That answer belongs to this other scenario: Branch-specific prefix updates flood every campus router; a proposed aggregate crosses two distinct WAN egress sites. It does not establish the necessary change in this case.
D:That answer belongs to this other scenario: A campus wants deterministic STP roots but all switches retain default bridge priorities. It does not establish the necessary change in this case.
E:This offered choice, “Prefix changes within a campus no longer cause unnecessary global churn while remote packets use the proper border”, addresses a separate concern. That answer belongs to this other scenario: Branch-specific prefix updates flood every campus router; a proposed aggregate crosses two distinct WAN egress sites. It does not establish the necessary change in this case.
Question 916
An IS-IS backbone suffers topology oscillation because a marginal core link repeatedly flaps. Choose THREE statements that form the design action, direct verification, and deployment safeguard. (Choose THREE.)
- Baseline LSP refresh, interface errors, and failover events before tightening detection timers.
- The neighbors reach FULL and application packets traverse without fragmentation problems.
- Align supported interface MTU and OSPF adjacency parameters rather than suppressing the mismatch blindly.
- After repairing the link, LSP churn falls and traffic reconverges on stable intended paths.
- Confirm end-to-end payload MTU and vendor hardware support before making both sides match.
- Use appropriate convergence design, link health remediation, and scoped metric or fast-failure detection without masking a physical fault.
Explanation
Correct Answers
A:Baseline LSP refresh, interface errors, and failover events before tightening detection timers. This applies directly to the reported network-design requirement.
D:After repairing the link, LSP churn falls and traffic reconverges on stable intended paths. This is the observable acceptance check for the change.
F:Use appropriate convergence design, link health remediation, and scoped metric or fast-failure detection without masking a physical fault. This is the corrective design for the stated topology.
Incorrect Answers
B:This offered choice, “The neighbors reach FULL and application packets traverse without fragmentation problems”, addresses a separate concern. This statement relates to a different requirement: Two OSPF neighbors on a routed core link are stuck in EXSTART/EXCHANGE and one endpoint uses an incompatible MTU. It does not address the condition described here.
C:This offered choice, “Align supported interface MTU and OSPF adjacency parameters rather than suppressing the mismatch blindly”, addresses a separate concern. This statement relates to a different requirement: Two OSPF neighbors on a routed core link are stuck in EXSTART/EXCHANGE and one endpoint uses an incompatible MTU. It does not address the condition described here.
E:This offered choice, “Confirm end-to-end payload MTU and vendor hardware support before making both sides match”, addresses a separate concern. This statement relates to a different requirement: Two OSPF neighbors on a routed core link are stuck in EXSTART/EXCHANGE and one endpoint uses an incompatible MTU. It does not address the condition described here.
Question 917
A multicast source is reachable through an interface other than the one receiving the packet, but the router still forwards it to all receivers. Select TWO statements that together define the best corrective design and its acceptance evidence. (Choose TWO.)
- Packets arriving on incorrect RPF interfaces are rejected and legitimate receiver traffic passes.
- Multicast forwarding resumes on the newly valid upstream with no persistent duplicates.
- Verify correct Reverse Path Forwarding behavior and IGP unicast route alignment for multicast sources.
- Provide an independently reachable out-of-band management network and approved emergency access process.
- Validate reconvergence of multicast RPF and join/prune state after unicast routing changes.
Explanation
Correct Answers
A:Packets arriving on incorrect RPF interfaces are rejected and legitimate receiver traffic passes. This is the observable acceptance check for the change.
C:Verify correct Reverse Path Forwarding behavior and IGP unicast route alignment for multicast sources. This applies directly to the reported network-design requirement.
Incorrect Answers
B:This offered choice, “Multicast forwarding resumes on the newly valid upstream with no persistent duplicates”, addresses a separate concern. That answer belongs to this other scenario: The RPF interface changes after a unicast route failover, but the multicast router retains stale upstream join state. It does not establish the necessary change in this case.
D:This offered choice, “Provide an independently reachable out-of-band management network and approved emergency access process”, addresses a separate concern. That answer belongs to this other scenario: A core router's production data plane fails, leaving SSH reachable only through the same failed core path. It does not establish the necessary change in this case.
E:This offered choice, “Validate reconvergence of multicast RPF and join/prune state after unicast routing changes”, addresses a separate concern. That answer belongs to this other scenario: The RPF interface changes after a unicast route failover, but the multicast router retains stale upstream join state. It does not establish the necessary change in this case.
Question 918
Backup 5G is installed at a factory but its data plan and APN firewall rules block VPN establishment after primary fiber failure. Choose THREE statements that form the design action, direct verification, and deployment safeguard. (Choose THREE.)
- Monitor data caps, power and radio signal as part of backup readiness.
- Record SLA impact and safe return criteria before enabling automatic restoration.
- Application sessions remain stable through short intermittent primary path disturbances.
- Validate backup access, overlay establishment and route activation under simulated primary loss.
- Introduce deliberate recovery policy or dampening to prevent repeated unstable failback.
- The required VPN tunnels and critical services establish over cellular during a failure exercise.
Explanation
Correct Answers
A:Monitor data caps, power and radio signal as part of backup readiness. This applies directly to the reported network-design requirement.
D:Validate backup access, overlay establishment and route activation under simulated primary loss. This is the corrective design for the stated topology.
F:The required VPN tunnels and critical services establish over cellular during a failure exercise. This is the observable acceptance check for the change.
Incorrect Answers
B:This offered choice, “Record SLA impact and safe return criteria before enabling automatic restoration”, addresses a separate concern. This statement relates to a different requirement: A dual-carrier WAN design changes to backup but automatically switches back on every momentary primary heartbeat recovery. It does not address the condition described here.
C:This offered choice, “Application sessions remain stable through short intermittent primary path disturbances”, addresses a separate concern. This statement relates to a different requirement: A dual-carrier WAN design changes to backup but automatically switches back on every momentary primary heartbeat recovery. It does not address the condition described here.
E:This offered choice, “Introduce deliberate recovery policy or dampening to prevent repeated unstable failback”, addresses a separate concern. This statement relates to a different requirement: A dual-carrier WAN design changes to backup but automatically switches back on every momentary primary heartbeat recovery. It does not address the condition described here.
Question 919
A company assigns IPv6 /127 links between routers but a proposed monitoring tool treats each link as a /64 SLAAC user LAN. Select TWO statements that together define the best corrective design and its acceptance evidence. (Choose TWO.)
- Set consistent IS-IS link metrics reflecting intended primary and backup capacity and verify resulting shortest paths.
- Router adjacencies form on the /127 links while end hosts receive appropriate /64 router advertisements on user LANs.
- Keep /127 point-to-point addressing for supported router links and use separate /64 allocations for conventional endpoint segments.
- Use a legitimately allocated private or global prefix at the remote site and reserve IPv4 link-local for local-only communication.
- Observed inbound paths trend toward ISP B from representative external monitors without assuming universal control.
Explanation
Correct Answers
B:Router adjacencies form on the /127 links while end hosts receive appropriate /64 router advertisements on user LANs. This is the observable acceptance check for the change.
C:Keep /127 point-to-point addressing for supported router links and use separate /64 allocations for conventional endpoint segments. This applies directly to the reported network-design requirement.
Incorrect Answers
A:That answer belongs to this other scenario: A network uses IS-IS with dual distribution routers and wants predictable traffic away from a low-bandwidth backup path. It does not establish the necessary change in this case.
D:That answer belongs to this other scenario: A remote office assigns clients addresses from 169.254.0.0/16 and expects them to be reachable through a routed WAN. It does not establish the necessary change in this case.
E:This offered choice, “Observed inbound paths trend toward ISP B from representative external monitors without assuming universal control”, addresses a separate concern. That answer belongs to this other scenario: A company wants most return traffic for its public prefix to enter ISP B rather than ISP A. It does not establish the necessary change in this case.
Question 920
A campus wants deterministic STP roots but all switches retain default bridge priorities. Choose THREE statements that form the design action, direct verification, and deployment safeguard. (Choose THREE.)
- Design an appropriate first-hop redundancy protocol with a shared virtual gateway and verified uplink tracking.
- Place primary and secondary STP root roles at the appropriate distribution devices for the planned VLAN sets.
- Root bridge elections and forwarding paths match the documented campus topology.
- Clients retain gateway reachability after either distribution switch fails.
- Verify root identity for every relevant VLAN or MST instance rather than one sample VLAN.
- Verify VLAN membership, upstream reachability and failure ownership before activating the virtual address.
Explanation
Correct Answers
B:Place primary and secondary STP root roles at the appropriate distribution devices for the planned VLAN sets. This is the corrective design for the stated topology.
C:Root bridge elections and forwarding paths match the documented campus topology. This is the observable acceptance check for the change.
E:Verify root identity for every relevant VLAN or MST instance rather than one sample VLAN. This applies directly to the reported network-design requirement.
Incorrect Answers
A:This offered choice, “Design an appropriate first-hop redundancy protocol with a shared virtual gateway and verified uplink tracking”, addresses a separate concern. This statement relates to a different requirement: A building has two independent distribution switches but hosts use the physical IP of one switch as their default gateway. It does not address the condition described here.
D:This offered choice, “Clients retain gateway reachability after either distribution switch fails”, addresses a separate concern. This statement relates to a different requirement: A building has two independent distribution switches but hosts use the physical IP of one switch as their default gateway. It does not address the condition described here.
F:This offered choice, “Verify VLAN membership, upstream reachability and failure ownership before activating the virtual address”, addresses a separate concern. This statement relates to a different requirement: A building has two independent distribution switches but hosts use the physical IP of one switch as their default gateway. It does not address the condition described here.
Designing Cisco Enterprise Networks (ENSLD) (300-420) Practice Tests
