Dividi l'indirizzo IPv4 in 4 numeri in Oracle sql

Potresti usare regexp_substr :

select ip,
       regexp_substr(ip, '\d+',1,1) as first_octet,
       regexp_substr(ip, '\d+',1,2) as second_octet,
       regexp_substr(ip, '\d+',1,3) as third_octet,
       regexp_substr(ip, '\d+',1,4) as fourth_octet
from  (select '10.20.30.40' AS ip from dual )ips;

Dimostrazione Rextester