A method and system for performing pre-authentication across inter-subnets. A pre-authentication request is received by a first access point associated with a first subnet from a mobile node requesting that is requesting pre-authentication with a second access point associated with a second subnet. The request is forwarded by the access point to a first authenticator that is the authenticator for the first subnet. The first authenticator obtains from a root infrastructure node the address for a second authenticator that is the authenticator for the second access point. The first authenticator then pre-authenticates the mobile node with the second authenticator by sending a message to the address for the second authenticator.