Methods and apparatus for portable network interfaces to manage authentication and license enforcement. A system may include a plurality of resource instances including a producer instance configured to implement a network-accessible service, and an authentication coordinator. The coordinator may assign an interface record to the service, wherein the interface record comprises an IP address and a set of security properties. The coordinator may configure the security properties to allow a client to request an attachment of the interface record to a selected resource instance, such that the selected resource instance is enabled to transmit network messages from the IP address using one or more physical network interfaces of the selected resource instance. The producer resource instance initiates authentication operations for the service, including at least one authentication operation based on the IP address of the interface record.