Du kan bruge 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;
Rextester Demo