Patent ID: 7764601

Claim:
A layer 2 switch switching circuit comprising: two layer 2 switches in a redundant configuration; and a plurality of cards for sending IP packets to each other through either one of said two layer 2 switches; each of said two layer 2 switches having a state signal delivery unit for delivering a state signal representing whether the layer 2 switch is in an active state or a standby state; each of said cards having a card controller for monitoring states of said two layer 2 switches based on state signals sent respectively from said two layer 2 switches, and switching between said two layer 2 switches as a destination of IP packets based on the monitored states; each of said two layer 2 switches including (i) an internal buffer for temporarily storing IP packets; and (ii) a switch controller for monitoring the state of the other layer 2 switch based on the state signal delivered from the other layer 2 switch, stopping sending IP packets to the corresponding card when a transition of the other layer 2 switch from the active state to the standby state is detected, and resuming sending IP packets to the corresponding card when the other layer 2 switch completes sending all IP packets held by the internal buffer thereof.