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5. Why subnetwork?

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 (saturate).

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:-

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