T4000 Switch Interface Board (SIB) Description
SIBs create the switch fabric for the T4000 Core Router. Each T4000 router contains five SIBs, located at the center rear of the chassis in the slots labeled SIB0 through SIB4 (top to bottom). One of the five SIBs acts as a backup to the remaining four SIBs. If a SIB fails, the backup SIB becomes active, and traffic forwarding continues without any degradation. When the failed SIB is replaced, it becomes the new backup. SIBs are hot-insertable and hot-removable.