Border Gateway Protocol (BGP) routing information packet includes an autonomous system (AS) path domain. The AS-Path filter specifies the matching condition for the AS path domain.
An AS_Path filter is used to filter routes based on the AS_Path attributes of BGP routes. If you do not want to receive routes of a specified AS number, configure an AS_Path filter based on the AS number. On a complex network, multiple ACLs or IP prefix lists must be configured to filter BGP routes, which is complicated. Configuring an AS_Path filter simplifies the configuration.
ip as-path-filter { as-path-filter-number | as-path-filter-name } { permit | deny } regular-expression