Cisco 400-007 - Cisco Certified Design Expert (CCDE v3.1)

Table Description automatically generated

C (SPF hold time): Controls the minimum amount of time between Shortest Path First (SPF) recalculations in link-state protocols like OSPF and IS-IS. This mechanism prevents frequent SPF runs due to rapid or transient topology changes, providing stability.

Other options explained:

A: Transmit delay affects LSA propagation but not routing protocol recalculation timing.

B: Throttle timers are related but primarily control LSA generation intervals.

D: Interface dampening suppresses flapping i

E (Infrastructure ACLs): iACLs control what traffic can reach network infrastructure devices, directly securing the data plane.

G (Routing Protocol Authentication): Prevents malicious or spoofed routing updates which directly protect data plane routing decisions.

Why other options are incorrect:

A: Warning banners are management plane hardening.

B: Redundant AAA is management/control plane hardening.

C: CPPr protects the control plane.

D: SNMPv3 secures management plane.

F: Disabling unused services typically applies to management plane or control plane, not data plane.

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A (Encryption + strong authentication) aligns most closely with Zero Trust’s emphasis on always verifying identity and protecting data as it moves across untrusted networks.

Data-in-motion encryption ensures confidentiality, and two-factor authentication ensures strict identity verification.

Why other options are incorrect:

B: Data-at-rest encryption is important but not as critical as controlling data in motion for Zero Trust.

C: Categorization helps in segmentation but is not the core Zero Trust principle.

D: High availability is a design requirement, not the primary Zero Trust security control.

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HIPAA requires integrity controls to prevent unauthorized data modification.

D (Technical integrity and transmission security): Ensures PHI data is protected against unauthorized alteration during storage and transmission.

This directly addresses the issue of data being altered without consent.

Why other options are incorrect:

A: Prevents unauthorized access but does not guarantee data integrity.

B: Administrative processes cover policies, not technical enforcement.

C: Focuses on physical device control, not data integrity.

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In PIM Sparse Mode, when the Last-Hop Router (LHR) receives multicast traffic on the shared tree (*,G), it performs an RPF check based on the RP address, not the multicast source address. In the diagram:

The LHR has IGP cost 10 towards the RP.

The shared tree (*,G) uses RP as the RPF target.

Since multicast traffic on (*,G) arrives on the interface toward RP (correct RPF interface), the RPF check succeeds.

Therefore, the multicast traffic is successfully switched toward the receivers.

This behavior is fully aligned with CCDE v3.1 multicast design principles, which emphasize clear understanding of RPF behavior both on shared trees (*,G) and source trees (S,G).

Why other options are incorrect:

A: The RPF check is not performed against the source in (*,G); it uses RP.

B: RPF checks are always performed, even on (*,G).

D: RPF is unrelated to the receiver address.