Personal computers are known to be highly usable as internet routers. To overcome their throughput limitations, a hardware accelerator can be employed. For the purposes of packet classification in the accelerator, we investigate a way to combine routing, level 2 addressing, and packet filtering into a single lookup structure. This paper describes the first part of the process: a method to combine routing and level 2 addressing to a single lookup. A formal model of routing and level 2 addressing is presented and used to prove correctness of the method and its equivalence to operating system behaviour.