RabbitCore RCM2200, Руководство по началу работы

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4–2 Using the TCP/IP Features RabbitCore RCM2200
Obtaining IP addresses to interact over an existing,
operating, network can involve a number of compli-
cations, and must usually be done with cooperation
from your ISP and/or network systems administra-
tor (if your company has one). For this reason, it is
suggested that the user begin instead by using a
direct connection between a PC and the RCM2200
board using an Ethernet crossover cable or a simple
arrangement with a hub. (A crossover cable should
not be confused with regular straight through
cables.) The hub and a wide variety of cables can
also be purchased from a local computer store.
In order to set up this direct connection, the user will
have to use a virgin PC (right out of the box), or dis-
connect a PC from the corporate network, or as yet
another approach install a second Ethernet adapter
and set up a separate private network attached to the
second Ethernet adapter. Disconnecting your PC
from the corporate network may be easy or nearly
impossible, depending on how it is set up. Mobile
PCs, such as laptops, are designed to be connected
and disconnected, and will present the least prob-
lem. If your PC boots from the network or is depen-
dent on the network for some or all of its disks, then
it probably should not be disconnected. If a second
Ethernet adapter is used, be aware that Windows
TCP/IP will send messages to one adapter or the
other, depending on the IP address and the binding
order in Microsoft products. Thus you should have
different ranges of IP addresses on your private net-
work from those used on the corporate network. If
both networks service the same IP address, then
Windows may send a packet intended for your pri-
vate network to the corporate network. A similar sit-
uation will take place if you use a dial-up line to
send a packet to the Internet. Windows may try to
send it via the local Ethernet network if it is also
valid for that network.
The following IP addresses are set aside for local
networks and are not allowed on the Internet:
10.0.0.0 to 10.255.255.255, 172.16.0.0 to
172.31.255.255, and 192.168.0.0 to
192.168.255.255.
The RCM2200 board uses a 10Base-T type of Eth-
ernet connection, which is the most common
scheme. The RJ-45 connectors are similar to U.S.
style telephone connectors, are except larger and
have 8 contacts.
An alternative to the direct connection using a cross-
over cable is a direct connection using a hub. The
hub relays packets received on any port to all of the
ports on the hub. Hubs are low in cost and are
readily available. The RCM2200 board uses 10
Mbps Ethernet, so the hub or Ethernet adapter must
be either a 10 Mbps unit or a 10/100 unit that adapts
to either 10 or 100 Mbps.
In a corporate setting where the Internet is brought
in via a high-speed line, there are typically machines
between the outside Internet and the internal net-
work. These machines include a combination of
proxy servers and firewalls that filter and multiplex
RCM2200
User’s PC
Ethernet
crossover
cable
Direct Connection
(Network of 2 computers)
RCM2200
Hub
Ethernet
cables
To additional
network
elements
Direct Connection Using a Hub
Board
Board