Patent ID: 7274703

Claim:
A network unit comprising: (a) a multiplicity of ports for transmitting and receiving data packets; (b) a bridging facility; and (c) a routing facility including at least two routing interfaces which when enabled allow the unit to route data packets and when disabled allow the unit to bridge but not route data packets; wherein said network unit has a multiplicity of mutually exclusive states including: (i) a master routing state in which the routing interfaces are enabled and the network unit broadcasts an advertisement including an address of the network unit; wherein on entry to said master routing state the network unit provides commands for enabling routing interfaces of other network units to which the network unit is connected; (ii) a listening state in which on receipt from another network unit of an advertisement including an advertised address corresponding to an address of said other network unit, the routing interfaces are disabled; (iii) a master bridging state wherein said router interfaces are disabled and in response to a predetermined absence of said advertisement can transition to said master routing state; (iv) a slave routing state wherein said router interfaces are enabled and said advertisement is not broadcast; and (v) a slave bridging state wherein said router interfaces are disabled and said advertisement is not broadcast; wherein in said slave bridging state the network unit provides commands for disabling routing interfaces of other network units to which the network unit is connected; and wherein in said slave bridging state the network unit is responsive to an external enabling command to transition from said slave bridging state to said slave routing state and to an external disabling command to transition from said slave routing state to said slave bridging state.