Private autonomous system (AS) numbers which range from 64512 to 65535 are used to conserve globally unique AS numbers. Globally unique AS numbers (1 - 64511) are assigned by InterNIC . These private AS number cannot be leaked to a global Border Gateway Protocol (BGP) table because they are not unique (BGP best path calculation expects unique AS numbers; see BGP Best Path Selection Algorithm for more information on BGP path selection). For this reason, a new feature was added in Cisco IOS® Software release 10.3 and later, which allows the stripping of private AS numbers out of the AS_PATH list before the routes are propagated to a BGP peer.