Thank you all for the help from ANS, MCI, BBN people. The trafic start flowing to/from ANS network. To recap my correspondense to them: the proper way to change route advertisement from /20 to /19: first add route object /19 to RADB advertise the new route /19 wait until it is propagated to the whole internet ( 3 days ) delete the old route object /20 stop advertise the old route /20 by doing this there should be minimal unreachable network. any comment, suggestion ? Thank you again for your help. Tony S. Hariman http://www.tsh.or.id Tel: +62(21)574-2488 Fax: +62(21)574-2481