Maintain the Infoblox ND-4000-NIGRID-DC platform under the ISP L3+ maintenance tier for one year. ND-MAIN-4000-NIGRID-DC-I21 identifies the annual maintenance entitlement associated with that designated NIGRID DC configuration. It is a service item rather than a separate hardware appliance, pairing a stated covered period with the ISP L3+ maintenance level. The covered platform designation matters because the service is tied to ND-4000-NIGRID-DC, including its NIGRID DC configuration. Use the complete covered-product designation when aligning maintenance with an installed platform. The one-year term is the defining duration of this service option, making it suitable where annual maintenance coverage is required for the specified system. ISP L3+ identifies the maintenance tier selected by this item. The tier name and covered product designation distinguish this service from maintenance options that may apply to different hardware configurations or service levels. This item establishes maintenance coverage for the named platform and period; it does not itself identify a response-time commitment, replacement arrangement, support channel, or additional hardware. Retain the full service code and the covered platform designation together when validating service scope for the installed environment.