3Com 3C840 - Manual (Page 169)

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.
Figure A–3 Example 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,
LAN 2
LAN 1 LAN 3
Bridge A Bridge D
840ug.book Page 7 Friday, July 7, 2000 2:23 PM