Maintain an Infoblox Network 4000 physical appliance with a one-year ISP L3+ maintenance service term. This entitlement is associated with the physical appliance platform rather than a virtual deployment, making it applicable where Network 4000 hardware remains part of the operational DNS, DHCP, IP address management, or related network-services environment. NT-MAIN-4000-MRI-S21 identifies the one-year maintenance offering with the ISP L3+ service designation. The term is tied to the Network 4000 physical platform, helping administrators retain the designated maintenance level throughout a defined annual period. It is a service entitlement rather than a replacement appliance, software license, or standalone network-services product. Select this maintenance service when the installed base includes an Infoblox Network 4000 physical appliance and the required coverage level is ISP L3+ for one year. The platform-specific designation matters: maintenance services must align with the appliance family and deployment type they cover. Retain the exact ordering code with the installed appliance records so the service term can be associated with the intended Network 4000 physical system.