300-420 Exam Dumps : Designing Cisco Enterprise Networks (ENSLD) v1.1

Service routes in OMP updates identify services that are available for centralized service insertion. In Cisco Catalyst SD-WAN, OMP does more than advertise ordinary VPN prefixes. It also carries TLOC routes, which describe transport locators, and service routes, which allow the fabric to steer traffic toward network services such as firewalls, intrusion prevention systems, or other centralized service nodes. This is how the SD-WAN control plane distributes enough information for WAN Edge routers to make policy-driven forwarding decisions without requiring each device to learn service attachment through a separate routing protocol. A service route is not used to describe the underlay transport itself, because that function is handled by TLOC information. It is also not a route to the orchestration plane or a remote management definition. The design value is that service insertion can be centrally advertised and controlled through OMP, then applied consistently through SD-WAN policy. Reference topics: Cisco SD-WAN OMP, service routes, TLOC routes, service insertion, centralized data policy.

The border node provides connectivity between the SD-Access fabric and networks external to the fabric. In Cisco SD-Access, fabric edge nodes connect endpoints, intermediate nodes provide underlay transport, and control-plane nodes maintain endpoint-to-location mappings. Border nodes sit at the boundary of the fabric and connect the overlay to external Layer 3 networks such as WAN, data center, Internet edge, shared services, or other fabrics. They de-encapsulate VXLAN traffic leaving the fabric and advertise or import reachability using VRFs and routing protocols. A border can be internal, external, or anywhere border depending on whether it connects to shared services, outside networks, or both. Intermediate nodes do not provide external fabric exit; they only transport traffic within the underlay. Edge nodes connect endpoints but are not normally the external gateway for the whole fabric. Control-plane nodes provide mapping services, not external connectivity. Reference topics: SD-Access border node, fabric exit, VRF mapping, external connectivity, overlay-to-underlay boundary.

BGP outbound route filtering is the correct solution because the enterprise wants control over which routes it receives without waiting for a provider change cycle each time the prefix set changes. Cisco BGP prefix-based ORF allows a receiving BGP speaker to send an inbound prefix-list filter to the remote peer, which then applies that list as an outbound filter. This reduces unwanted routing updates before they cross the session and lets the enterprise update the desired prefixes locally when business requirements change. Requesting only fixed prefixes from the ISP would work initially but fails the flexibility requirement because the provider has a two-week change process. Requesting a full table and filtering inbound would provide flexibility but wastes memory and CPU on the customer router because all routes are still received before filtering. A maximum-prefix limit does not select the correct routes. ORF is therefore the scalable operational design for receiving a default route and selected prefixes with minimal provider involvement. Reference topics: BGP ORF, prefix-based filtering, inbound route control, ISP peering design, routing table scale.