Filter list – using as-path access list
ip as-path access-list 1 permit _3561$
ip as-path access-list 2 deny _35$
ip as-path access-list 2 permit .*
neighbor 171.69.233.33 remote-as 33
neighbor 171.69.233.33 filter-list 1 in
neighbor 171.69.233.33 filter-list 2 out
Listen to routes originated by AS 3561. Implicit deny everything else inbound.
Don’t announce routes originated by AS 35, but announce everything else (outbound).