A mobile router is configured for generating a local router prefix (i.e., a null or invalid address prefix that is not reachable via a wide area network) for use by mobile nodes that attempt to attach to the mobile router. The mobile router attaches to an attachment router using a care-of address with an attachment router address prefix, and outputs a router advertisement message that specifies the null address prefix. Upon receiving a message from a mobile host that includes a source address field specifying a mobile host care-of address that includes the null address prefix, the mobile router adds the mobile host care-of address to a reverse routing header and inserts its own care-of address into the source address field. The message is output to its destination with the reverse routing header, ensuring the IPv6 address of the mobile router remains anonymous in the wide area network.