A router for interconnecting external devices coupled to the router. The router comprises a switch fabric and a plurality of routing nodes coupled to the switch fabric. Each routing node is capable of transmitting data packets to, and receiving data packets from, the external devices and is further capable of transmitting data packets to, and receiving data packets from, other routing nodes via the switch fabric. The router also comprises a control processor for comparing the N most significant bits of a first subnet address associated with a first external port of a first routing node with the N most significant bits of a second subnet address associated with a second external port of the first routing node. The router determines a P-bit prefix of similar leading bits in the first and second subnet addresses and transmits the P-bit prefix to other routing nodes.