Cisco 300-420 Exam With Confidence Using Practice Dumps

The correct IS-IS design combines tuned SPF/PRC behavior with a proper Level 1 and Level 2 hierarchy. Reducing SPF and PRC intervals, within platform and stability limits, helps routers react more quickly to topology changes after a link failure. However, fast timers alone are not enough; the hierarchy must contain instability so physical link flaps in the access layer have limited impact on the rest of the network. Access routers should form Level 1 adjacencies inside their local area, while aggregation routers should operate as Level 1/Level 2 routers to connect the access area to the Level 2 backbone. This design gives access routers a simple local view and uses aggregation as the interarea boundary. Running all access and aggregation routers as L1/L2 across the network increases the size of the backbone and exposes more routers to wider flooding, which is the opposite of the requirement. Redistributing Internet routes into Level 1 is also poor design because it bloats the access area. Therefore, the right choices are C and E. Reference topics: IS-IS hierarchy, L1/L2 design, SPF and PRC tuning, access-layer convergence, fault containment.

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.

Scalable groups provide intra-VN traffic filtering and control in Cisco SD-Access. Within a virtual network, macro segmentation separates routing tables, but endpoints inside the same VN may still need policy control based on identity, role, or security posture. Cisco SD-Access uses scalable group tags and scalable group ACLs to implement group-based policy. This allows policy to be expressed as user or device group relationships instead of only subnet-based ACL entries. The result is microsegmentation inside the virtual network, where traffic between groups can be permitted or denied consistently across the fabric. MAC ACLs are limited Layer 2 filters and do not provide the identity-based policy model required for SD-Access. Prefix lists are route-filtering tools, not intra-VN access-control mechanisms. Service policies are used for QoS or traffic treatment and do not define group-based segmentation. Scalable groups are therefore the correct policy construct for intra-VN filtering in the fabric. Reference topics: Cisco SD-Access policy, scalable groups, SGT, SGACL, microsegmentation, intra-VN control.