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

Route leaking on R13 and R9 is required so the Level 1 area can make a better exit decision toward the server. In an IS-IS hierarchy, Level 1 routers know detailed topology only inside their own area. For destinations outside the area, they normally follow the closest attached Level 1/Level 2 router, which can produce suboptimal latency when another exit has a better end-to-end path. Route leaking selectively injects more specific Level 2 reachability information into Level 1, allowing routers in the New Office area to evaluate a better path instead of blindly following the nearest attached-bit exit. Changing metric style on R8 alone does not import the external-area route information needed for better path selection. A static route could force a path but would not be a scalable dynamic IS-IS design. Making R8 Level 1/Level 2 does not solve the need to expose the relevant route through the correct area boundary. Reference topics: IS-IS Level 1 and Level 2, attached bit, route leaking, interarea optimization, latency-aware routing.

The branch subnets must each support up to 200 hosts, so /120 is the correct IPv6 prefix length from the available options. A /120 provides 256 IPv6 addresses, which satisfies the 200-host requirement. A /121 provides only 128 addresses, which is not enough. The parent block is 2a01:0c30:0016:7009::3800/118. A /118 has 10 host bits, so it contains 1024 addresses and spans from ::3800 through ::3bff. The valid /120 boundaries inside that parent are ::3800/120, ::3900/120, ::3a00/120, and ::3b00/120. From the listed choices, 2a01:0c30:0016:7009::3a00/120 and 2a01:0c30:0016:7009::3b00/120 both fall inside the parent allocation and provide enough address capacity. The /121 options are too small, and ::3c00/120 is outside the /118 parent range. This is a straightforward IPv6 prefix-boundary and capacity calculation. Reference topics: IPv6 subnetting, prefix length, address block boundaries, branch address planning.

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.