Calculate supernets to /16 in Oracle SQL

This bit of SQL calculates all the supernet addresses (to /16) for a given IP address (and mask) in Oracle. Supernet addresses are the 'containing' IP Addresses based on powers of 2, so a /30 address covers 2^(32-30) addresses (or 4 IPs). A /26 address covers 2^(32-26) addresses (64 IPs). This works on Oracle 9, 10 and 11. If your version does not support regexp_replace there are some commented fields that utilise some instr calls.

select 
lvl supernet_mask, 
ip, 
regexp_substr(ip,'^\d+\.\d+\.') || resl2 || '.' || resl supernet
from
(
select 
  lvl, ip, mask, q3,q4,
  case when lvl > 24 then
    null
  else 
    0 
  end supernet
  , 
  floor(q4/(power(2,32-lvl))) * power(2,32-lvl) resl 
  , 
  CASE WHEN lvl <= 24 then 
    floor(q3/(power(2,24-lvl))) * power(2,24-lvl) 
  ELSE 
    Q3
  END resl2
from
(
select lvl, ip, mask
, to_number(regexp_substr(ip,'\d+',1)) q1
, to_number(regexp_replace(ip,'(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})','\2')) q2
, to_number(regexp_replace(ip,'(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})','\3')) q3
, to_number(regexp_replace(ip,'(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})','\4')) q4
/* -- if your version does not support regexp_replace
, to_number(substr(ip,1,instr(ip,'.',1,1)-1)) q1
, to_number(substr(ip,instr(ip,'.',1,1)+1,instr(ip,'.',1,2 )-instr(ip,'.',1,1)-1 ))  q2
, to_number(substr(ip,instr(ip,'.',1,2)+1,instr(ip,'.',1,3 )-instr(ip,'.',1,2)-1 )) q3
, to_number(substr(ip,instr(ip,'.',1,3)+1)) q4
*/
from 
(
select 33 - level lvl,'203.63.104.108' ip,30 mask from dual connect by level <= 17 union
select 33 - level lvl,'203.63.104.12' ip,30 mask from dual connect by level <= 17 union
select 33 - level lvl,'203.63.104.124' ip,30 mask from dual connect by level <= 17 union
select 33 - level lvl,'203.63.104.144' ip,30 mask from dual connect by level <= 17 
) x
where mask >= lvl
) xx order by ip, lvl desc
) xxx