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

Graceful restart and nonstop forwarding designs depend on preserving forwarding continuity during a control-plane processor switchover. Cisco Stateful Switchover provides the mechanism for a standby route processor or supervisor to maintain synchronized state so it can assume control when the active processor fails. When SSO is combined with NSF or graceful restart capabilities in routing protocols, neighboring devices can continue forwarding traffic while the restarting device preserves or rebuilds control-plane adjacencies. Cisco Express Forwarding is required for fast data-plane forwarding, but CEF alone does not provide route processor state synchronization after processor failure. Virtual Switch System is a chassis or switching architecture that can provide high availability in certain campus designs, but it is not the required feature named by graceful restart recovery. Bidirectional Forwarding Detection is a failure-detection protocol used to detect path or neighbor failures quickly; it does not recover a failed processor. Therefore, the feature that must be incorporated for graceful restart recovery from processor failure is Stateful Switchover. In a resilient enterprise design, SSO, NSF, and protocol graceful restart are coordinated to reduce outage impact.

Implementing network summarization on the edge routers is the correct EIGRP design action to reduce query range and improve convergence. In EIGRP, when a route is lost and no feasible successor exists, DUAL sends queries to neighbors. If the network is large or poorly summarized, those queries can propagate widely and increase convergence time. Hierarchical addressing allows each office or edge block to advertise a summary instead of many specific prefixes. If a specific subnet inside an office fails, the summary can remain stable toward the rest of the network, preventing the failure from triggering unnecessary queries across the dark-fiber interoffice topology. Stub routing can also reduce query scope, but the option says to configure stub areas on non-edge routers, which is not the right EIGRP terminology or placement. Different EIGRP processes add redistribution complexity, and route filtering alone does not provide the same clean convergence boundary as summarization. Reference topics: EIGRP summarization, DUAL query scope, hierarchical addressing, convergence optimization, dark-fiber campus routing.

VRRP object tracking allows the effective priority of a VRRP router to change when a tracked object changes state. Cisco documentation states that VRRP object tracking ensures the best VRRP router is master by altering VRRP priorities according to tracked objects such as interface or IP route states. This directly supports answer A. It also supports answer D, because VRRP can track interfaces and routes through the tracking process. The priority does not have to remain fixed; object tracking is specifically designed so a router can lower its priority when an uplink, route, or critical dependency fails. A VRRP group is not limited to one tracked object in modern Cisco implementations, so option C is too restrictive. VRRP does not support only interface tracking; route tracking is also a common use case, especially when the LAN interface is still up but upstream reachability has failed. In a resilient campus or branch gateway design, object tracking prevents a router from remaining master when it no longer has a valid upstream path, improving deterministic failover.