The following is an example of BGP path filtering by neighbor. The routes that pass as-path access list 1
will get weight 100. Only the routes that pass as-path access list 2 will be sent to 193.1.12.10.
Similarly, only routes passing access list 3 will be accepted from 193.1.12.10.

router bgp 200
neighbor 193.1.12.10 remote-as 100
neighbor 193.1.12.10 filter-list 1 weight 100
neighbor 193.1.12.10 filter-list 2 out
neighbor 193.1.12.10 filter-list 3 in
!
!
ip as-path access-list 1 permit _109_
ip as-path access-list 2 permit _200$
ip as-path access-list 2 permit ^100$
ip as-path access-list 3 deny _690$
ip as-path access-list 3 permit .*