1. An apparatus for authenticating a computing device over a network, the apparatus comprising: a network interface that is coupled to the network for receiving one or more packet flows therefrom; a processor; and a computer readable medium having stored thereon one or more sequences of instructions which, when executed by the processor, cause the processor to carry out the steps of: generating a first binding between a first source address and one or more roles of a user accessing the network via a device coupled to the network, wherein the first source address is currently assigned to the device; distributing the first binding associated with the first source address to a filter node; responsive to a determination that the user is associated with a new source address, generating a new binding to associate the new source address with the one or more roles for the user; and distributing the new binding to the filter node.