What must be in place to achieve a 99.99% SLA for High Availability (HA)?

To achieve a 99.99% Service Level Agreement (SLA) for High Availability (HA), having two interfaces is essential. This configuration allows for redundancy and helps ensure continuous operation even if one interface fails. In a networking context, especially within cloud environments, redundancy is a crucial principle to maintain service availability.

By employing two interfaces, a system can route traffic through an active interface while providing a backup path in the event of failure. This dual interface setup supports failover capabilities, minimizing downtime and keeping services accessible to users.

Single interfaces lack the necessary redundancy, leading to a potential single point of failure. Having no interfaces would mean there is no connection available, rendering the service unusable. Using three interfaces could provide additional fault tolerance but is typically more than necessary for achieving a high availability metric of 99.99%, which can effectively be maintained with just two redundant paths.