300-420 Exam Dumps : Designing Cisco Enterprise Networks

Affinity is the Cisco SD-WAN feature used to minimize TLOC and control connections and reduce strain on vSmart controllers. Cisco documentation explains that establishing affinity between controllers and edge devices allows the operator to control overlay scaling by limiting which controllers an edge device can establish control connections with. In large deployments, unrestricted connections between every WAN Edge and every controller can create unnecessary state and operational load. Affinity lets the design distribute edge connections across controllers and data centers while still preserving redundancy through primary and backup controller relationships. Color identifies the transport type or behavior associated with a TLOC, but it does not reduce controller connection scale by itself. Control-direction and control-connections are not the feature names that provide the scaling function described in the question. A well-designed SD-WAN control plane uses affinity, controller groups, and redundancy planning to keep the overlay scalable and predictable. Reference topics: Cisco SD-WAN affinity, vSmart controller scale, TLOC connections, control-plane redundancy, overlay scaling.

Cisco SD-WAN uses the vSmart controller as the control-plane component that distributes the information needed for secure data-plane tunnel establishment. Before WAN Edge devices build full-mesh IPsec tunnels, they must learn reachability and security information through the SD-WAN control plane. Cisco documentation describes the vSmart controller as the centralized control-plane element that exchanges OMP routes, policy, TLOC information, and security parameters with WAN Edge routers. In the traditional SD-WAN key-exchange model, vSmart sends IPsec encryption keys to edge devices so the data plane can be secured without each edge independently negotiating IKEv2 with every other edge. vManage is the management platform and is not the key exchange point. vBond performs orchestration, authentication assistance, and NAT traversal during onboarding, but it is not the data-plane key server. IKEv2 may be used in specific newer or configured security models, but the typical Cisco SD-WAN overlay relies on vSmart for scalable key distribution. Reference topics: Cisco SD-WAN control plane, vSmart, OMP, IPsec key distribution, WAN Edge security.

In a Cisco SD-Access fabric, DHCP relay design must account for the fact that endpoints can attach to different fabric edge nodes while using consistent anycast gateway behavior. DHCP Option 82 is important because it inserts relay-agent information that allows the DHCP infrastructure to identify where the DHCP request originated. This enables the correct address scope and policy context to be selected for the endpoint even when the gateway address is anycast across multiple fabric edges. Cisco SD-Access DHCP guidance emphasizes the use of relay information so centralized DHCP services can assign the correct address based on fabric location and endpoint context. DHCP relay is not simply enabled on border nodes, and subnets should not be stretched across fabric edges by placing DHCP servers on borders. DHCP servers do not require a special proprietary SD-Access extension in the sense described by the incorrect option; they use standard relay information such as Option 82. Therefore, the key design consideration is enabling DHCP Option 82 so the circuit information maps the request to the fabric node where it originated.