RabbitCore RCM2200, Руководство по началу работы

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Getting Started Manual Using the TCP/IP Features 4–3
Internet traffic. In the configuration below, the
RCM2200 board could be given a fixed address so
any of the computers on the local network would be
able to contact it. It may be possible to configure the
firewall or proxy server to allow hosts on the Inter-
net to directly contact the controller, but it would probably be easier to place the controller directly on
the external network outside of the firewall. This
avoids some of the configuration complications by
sacrificing some security.
If your system administrator can give you an
Ethernet cable along with its IP address, the
netmask and the gateway address, then you
may be able to run the sample programs with-
out having to setup a direct connection
between your computer and the RCM2200
board. You will also need the IP address of the
nameserver, the name or IP address of your
mail server, and your domain name for some
of the sample programs.
4.3 IP Addresses Explained
IP (Internet Protocol) addresses are expressed as 4
decimal numbers separated by periods, for example:
216.103.126.155
10.1.1.6
Each decimal number must be between 0 and 255.
The total IP address is a 32-bit number consisting of
the 4 bytes expressed as shown above. A local net-
work uses a group of adjacent IP addresses. There
are always 2
N
IP addresses in a local network. The
netmask (also called subnet mask) determines how
many IP addresses belong to the local network. The
netmask is also a 32-bit address expressed in the
same form as the IP address. An example netmask
is:
255.255.255.0
This netmask has 8 zero bits in the least significant
portion, and this means that 2
8
addresses are a part
of the local network. Applied to the IP address
above (216.103.126.155), this netmask would indi-
cate that the following IP addresses belong to the
local network:
216.103.126.0
216.103.126.1
216.103.126.2
etc.
216.103.126.254
216.103.126.255
The lowest and highest address are reserved for spe-
cial purposes. The lowest address (216.102.126.0) is
used to identify the local network. The highest
address (216.102.126.255) is used as a broadcast
address. Usually one other address is used for the
address of the gateway out of the network. This
Hub(s)
Firewall
Proxy
Server
T1 in
Adapter
Ethernet Ethernet
Network
RCM2200
Board
Typical Corporate Network