Maintain continuity for eligible Infoblox DNS infrastructure through an annual ISP Level 3+ maintenance service. This offering applies to supported DNS systems that require ongoing maintenance coverage rather than replacement hardware. Its stated service tier gives administrators a clear coverage designation when maintaining DNS services that are central to name resolution, application access, and network operations. PT-MAIN-4K-10GEADNSGRID-AC-S21 provides a one-year service term at the stated ISP Level 3+ tier. Select it when the covered Infoblox DNS system requires annual maintenance renewal at that tier. Keep the service designation aligned with the equipment being covered, since maintenance eligibility depends on the specific system and its current service status. The annual duration distinguishes this option from longer-term maintenance periods, while the ISP Level 3+ designation differentiates it from offerings with other service levels. It is a maintenance service rather than a physical network appliance, so interface count, throughput, rack dimensions, and power requirements do not apply. The service is suited to environments where operational DNS infrastructure must remain under active maintenance coverage for the next 12 months.