Bernhard Kuemel wrote in a message to Mike Bilow:
 MB> IP addresses are simply 32-bit numbers.  They are by convention split
 BK> I read that in DNS there are reasons (reverse DN lookup?)
 BK> that limit subnetting to byte boundary. Then a different
 BK> paragraph said, nowadays subnetting is not limited to byte
 BK> boundary. Now, are there limitations? I know, ISPs offer eg
 BK> 16 IP-addresses, so subnetting below byte boundary is actual
 BK> practice. 
Subnetting and DNS are different things.  IP addresses are mapped into a 
pseudo-domain, the "IN-ADDR.ARPA" domain, for reverse mapping purposes.  This 
happens to be done on an octet boundary.  Internic still assigns blocks of IP 
addresses on octet boundaries, and they are therefore always managed by the 
same (or at least a closely related) administrative entity which provides the 
reverse lookup.  However, DNS issues have nothing to do with routing, and 
subnetting is a routing issue.
 
-- Mike
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