3Com 3C840 manual Network Organization, Structure, and Physical Layout A-7

Network Organization, Structure, and Physical Layout A-7

The Internet The protocol adopted by the Defense Data Network (DDN) for the Internet, is based on obtaining and abiding by, a registered Internet address range. This makes a router the ideal choice for accessing the Internet. Unfortunately, new applicants are only likely to get a Class C registered Internet address, preventing more than 254 connections on one bridged IP LAN.

Routing IP Running a bridged network allows workstations to communicate directly between one another. A PC user wishing to communicate with a remote network server is totally unaware of any intervening bridges. This is known as transparent operation.

	LAN 2
Bridge A	Bridge D
LAN 1	LAN 3

Figure A–3Example Network

It is important to understand that in a bridged network the addressing structure for IP relates to a single network. If the units above were bridges and not routers, then an IP node on LAN A could, for example, have an address 140.56.10.1, the node on LAN B an address of 140.56.10.2, and the node on LAN C, an address of 140.56.10.3. All the nodes, therefore,