Pass the Cisco CCDE v3.0 400-007 Questions and answers with CertsForce

A (MSDP - Multicast Source Discovery Protocol):MSDP allows different autonomous systems to share multicast source information while maintaining their own PIM Sparse Mode domains. It simplifies interdomain multicast routing without requiring full mesh peering or shared RPs between domains.

Other options explained:

B: SSM does not require MSDP but limits use to source-specific groups.

C: MPLS is a transport technology, not multicast control-plane solution.

D: PIM-SM is used within a domain, not across multiple autonomous systems.

B (Micro loops):OSPF Loop-Free Alternates (LFA) pre-calculate backup next-hops to reduce transient micro loops during the convergence process when primary routes fail.

Other options explained:

A: DTP relates to trunk negotiation, not loop prevention.

C: STP handles Layer 2 loops.

D: REP is a Cisco Layer 2 redundancy protocol, unrelated to OSPF loop prevention.

B (Use only secure protocols): Management and administrative access to Internet edge routers must use secure protocols (SSH, SNMPv3, HTTPS) to prevent interception or unauthorized access.

E (Restrict administrative access): Limiting administrative access via interface ACLs and clear login banners ensures that only authorized personnel can access the system, satisfying compliance and security requirements.

Other options explained:

A: Filtering infrastructure IP space is good hygiene but not directly related to compliance.

C: Logging is valuable for operations and incident response but not a compliance control by itself.

D: EBGP advertisements relate to routing policy, not compliance regulation.

When multiple virtualized network zones (such as VRFs, virtual firewalls, or logical partitions) are consolidated onto a single physical device, the primary concern is:

A (Fate sharing): A single hardware failure, software crash, or resource exhaustion event could simultaneously impact all virtualized zones, creating a shared risk across multiple otherwise isolated services.

Other options explained:

B: CPU resource allocation can be controlled via resource management but is not the primary risk.

C: Congestion control is typically a traffic engineering issue, not a virtualization risk.

D: Security isolation can be maintained through proper virtualization boundaries.

E: Bandwidth can be managed through QoS and resource allocation.

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A (Design expecting outages and attacks):In WAN design, resiliency requires assuming that failures and attacks will occur. This drives the use of redundancy, diverse paths, and proactive failure mitigation techniques.

Other options explained:

B/C/D: While important, these focus on operational efficiency rather than core resiliency principles.

C (QoS policy propagation with BGP - QPPB):Allows QoS policies to be dynamically applied based on BGP routing information, integrating policy control into routing decisions.

D (Remote black-holing trigger):Enables dynamic mitigation of attacks (e.g., DDoS) by injecting blackhole routes through BGP to selectively drop malicious traffic upstream.

Other options explained:

A/B/E: Static policy mechanisms that lack dynamic flexibility and responsiveness in modern service provider designs.

The IS-IS Overload Bit allows a router to signal to its peers that it should be temporarily excluded from SPF calculations for transit traffic:

A: The Overload Bit can be automatically set at startup (known as " startup overload " ) to allow the router sufficient time to converge IGP, BGP, and stabilize protocols before accepting transit traffic.

D: The bit can remain set until all dependent protocols have converged and the router is fully operational.

Why other options are incorrect:

B: The router’s directly connected prefixes remain reachable; only transit path calculations exclude the overloaded node.

C: MPLS-TE does not automatically reoptimize tunnels based on the Overload Bit.

E: There is no specific restriction preventing Overload Bit usage on Route Reflectors.