400-007 Exam Dumps - Cisco CCDE v3.0 Questions and Answers

BGP-LS (BGP Link-State) distributes IGP topology information using BGP. When used in multi-area or multi-domain networks, BGP-LS allows for a centralized controller to receive topology information in a scalable way. BGP inherently runs over TCP, which provides reliable, ordered delivery using built-in flow control mechanisms.

The use ofTCP-based flow controlensures that even in large-scale networks where significant link-state information is exchanged, the flow of data between BGP peers remains efficient, controlled, and buffered according to the receiver ' s capacity. This makes it ideal for transporting massive amounts of LS data across wide areas and into SDN controllers for applications like traffic engineering or path computation.

Why other options are incorrect:

A, B, and C refer to mechanisms that are not implemented or leveraged by BGP.

TCP-based flow control is the only valid flow-control mechanism used in BGP sessions.

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When logical VRF separation is based on fields like IP address ranges or packet characteristics (such as packet length), the most scalable solution is:

Policy-Based Routing (PBR): This allows traffic to be classified and forwarded into the correct VRF based on flexible match conditions like source IP address, destination IP address, or packet size.

Why other options are incorrect:

A: Static route leaking lacks flexibility and scalability for dynamic classification.

C: OSPF per VRF handles control-plane separation, but not data-plane traffic classification.

D: MP-BGP is used for control-plane VPN route exchange, but not for VRF selection based on traffic attributes.

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B: Service chaining in NFV can create suboptimal traffic flows depending on how virtualized functions are distributed.

E: NFV often requires orchestration platforms for lifecycle management, scaling, and automation of VNFs.

Why other options are incorrect:

A: Bandwidth utilization may not necessarily increase.

C: NFV enables use of commodity servers, not high-end routers.

D: OpenFlow is not mandatory for NFV deployment.

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A (Scaling challenges for services):Centralized SDN controllers may experience scalability challenges for distributed services like DHCP and load balancing since these often require real-time responsiveness and distributed service locality.

D (Latency in reactive handling):Centralized controllers may introduce additional latency during reactive PACKET_IN event handling as control decisions traverse the control plane before forwarding happens.

Other options explained:

B: Centralized controllers still present failure domain risks; high-availability must be explicitly designed.

C: Smart NICs operate primarily at the host level, often independently of centralized SDN controllers.

E: Legacy equipment often lacks support for many SDN southbound APIs.

A picture containing table Description automatically generated

IPv4:

Host Registration - IGMP

Router Registration - PIM-DM, PIM-SM, SSM, BIDIR

Inter-Domain Source Discovery - MSDP

IPv6:

Host Registration - MLD

Router Registration - PIM-SM, SSM, BIDIR

In data center migration scenarios, when legacy and VXLAN EVPN networks are connected for host mobility, a critical step is to ensure a seamless Layer 3 gateway handoff. This is typically achieved using VRRP (or HSRP) where both the old and new gateways share the same virtual IP.

The final step involves:

Increasing the VRRP priority on the new VXLAN-enabled infrastructure to make it the active default gateway.

Ensuring that hosts retain their original default gateway (no reconfiguration required).

Only after the new gateway is active, the legacy SVIs can be gracefully shut down.

This method ensures no packet loss or disruption to host connectivity during or after migration.

It aligns with CCDE v3.1 under the “Network Architecture Principles” domain, particularly for data center transformation, operational consistency, and seamless L2–L3 handoff design patterns.