Private AS Number Removal from Route Updates

Private AS numbers are AS numbers in the range 64512 through 65534. You can remove private AS numbers from the AS path attribute in updates that are sent to external BGP (EBGP) neighbors. Possible reasons for using private AS numbers include:
  • The remote AS does not have officially allocated AS numbers.

  • You want to conserve AS numbers if you are multihomed to the local AS.

Private AS numbers should not be advertised on the Internet. Private AS numbers can be used only locally within an administrative domain. Therefore, when routes are advertised out to the Internet, the routes can be stripped out from the AS paths of the advertised routes using this feature.