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Distributor of Digi International: Excellent Integrated System Limited
Datasheet of 101-1274 - KIT DEV STANDARD RCM5700
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F.2.2 How IP Addresses are Used
The actual hardware connection via an Ethernet uses Ethernet adapter addresses (also called
MAC addresses). These are 48-bit addresses and are unique for every Ethernet adapter manufac-
tured. In order to send a packet to another computer, given the IP address of the other computer, it
is first determined if the packet needs to be sent directly to the other computer or to the gateway.
In either case, there is an Ethernet address on the local network to which the packet must be sent.
A table is maintained to allow the protocol driver to determine the MAC address corresponding to
a particular IP address. If the table is empty, the MAC address is determined by sending an Ether-
net broadcast packet to all devices on the local network asking the device with the desired IP
address to answer with its MAC address. In this way, the table entry can be filled in. If no device
answers, then the device is nonexistent or inoperative, and the packet cannot be sent.
Some IP address ranges are reserved for use on internal networks, and can be allocated freely as
long as no two internal hosts have the same IP address. These internal IP addresses are not routed
to the Internet, and any internal hosts using one of these reserved IP addresses cannot communi-
cate on the external Internet without being connected to a host that has a valid Internet IP address.
The host would either translate the data, or it would act as a proxy.
Each MiniCore module has its own unique MAC address, which consists of the prefix 0090C2
followed by a code that is unique to each MiniCore module. For example, a MAC address might
be 0090C2C002C0.
TIP: You can always obtain the MAC address on your module by running the sample program
DISPLAY_MAC.C from the SAMPLES\TCPIP folder.
MiniCore RCM5700/RCM6700 User's Manual
digi.com
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