A school district has two WAN Edge routers sharing one LAN gateway address for 300 classroom devices, requiring subsecond failover if the primary access switch link or router fails. Templates must keep both routers consistent. Which VRRP design should the engineer implement on the service side for LAN redundancy?

The design with the same VRRP group and virtual IP on both service VPN interfaces gives all classroom devices one LAN gateway. The primary’s higher priority establishes the intended master, tracking can lower its priority when the access-switch link fails even if the router remains up, and a subsecond advertisement timer supports the required rapid failover. Templates keep these settings consistent across both routers. Using standard-interval advertisements with tracking and higher primary priority can reduce control traffic, but detection may take too long to meet the subsecond requirement. Using a subsecond timer without tracking can detect a router failure quickly, but a primary whose LAN link fails may remain master despite lacking a working path, preventing effective failover. Applying the otherwise appropriate group, virtual IP, priority, tracking, and timer through individually customized router CLI may work initially, but bypasses the required shared templates and risks configuration drift that can disrupt mastership or preemption. Exam caveat: distinguish service-side LAN gateway redundancy from overlay resiliency; overlay failover does not itself provide hosts with a default gateway. Practical check: verify that clients use the virtual IP, confirm the routers’ master and backup roles and priorities, then shut the primary LAN interface and confirm a subsecond role change with only one or two pings lost.