16
C
R
D
2
7
0
0
-
4
2
0
0
E
Enter the new Terminal 2, IP addresses, at the prompt.
l.
Select C to access the Terminal 3 IP addresses prompt.
Enter the new Terminal 3, IP addresses, at the prompt.
m. Select D to access the Terminal 4 IP addresses prompt.
Enter the new Terminal 4, IP addresses, at the prompt.
4. Select Q to return to the main Cradle Utilities menu.
5. Select F to reset cradle and write values to Flash memory.
Network Address Translation (NAPT)
In both DHCP and static mode, the cradle assigns private IP
addresses to each terminal and performs Network Address
Translation (NAPT) on all TCP/IP and UDP/IP packets as they
transmit through the cradle between the outside network and the
cradle’s private network. The terminals are assigned private
addresses specified in options A-E in the Public network menu
above.
The cradle modifies one IP address and port number pair inside a
TCP/IP and UDP/IP packet header. Those packets going to the
outside network have their source address translated to the IP
address of the cradle and their source port changed to a unique
port number associated with the cradle slot it came from.
Conversely, packets designated to the cradle’s private network
have their destination IP address and port number mapped to the
equivalent private network IP address and port number. The
differences in the port numbers distinguish between packets for
different slots in the cradle. The benefit of both IP address and port
translation is that multiple slots can simultaneously share the one
network IP address of the cradle.
Accessing the outside network with the CRD2700-4200E is not the
same as a direct connection to the outside network. When using
NAPT, many network services do not function at all. Since NAPT
modifies addresses in TCP/IP and UDP/IP headers, it is
