The reasons behind sub-networking date back to the early
specification of IP - where just a few sites were running on
Class A network numbers, which allow for millions of connected
hosts. It is obviously a huge traffic and administration problem
if all IP computers at a large site need to be connected to the
same network: trying to manage such a huge beast would be a
nightmare and the network would (almost certainly) collapse
under the load of its own traffic Enter sub-networking: the A
class IP network address can be split up to allow its
distribution across several (if not many) separate networks. The
management of each separate network can easily be delegated as
well. This allows small, manageable networks to be established -
quite possibly using different networking technologies.
Remember, you cannot mix Ethernet, Token Ring, FDDI, ATM etc on
the same physical network - they can be interconnected, however!
Other reasons for sub-networking are:- - Physical site layout
can create restrictions (cable run len