When configuring VRRP to avoid a black hole after the primary transport fails, what should be tracked to achieve the fastest failover to the standby?

Prefix-list tracking is the most effective method for fast VRRP failover in SD-WAN when a primary transport fails. By tracking the reachability of specific prefixes (e.g., the next-hop IP address of the primary transport), VRRP can quickly detect a loss of connectivity and trigger a failover to the standby router. This is faster than relying on OMP (Overlay Management Protocol) convergence, which can take longer as it involves control plane updates across the SD-WAN fabric. A higher group ID number is irrelevant to failover speed. A lower timer interval can accelerate detection but doesn't specifically target transport failures as precisely as prefix-list tracking.