3Com 3036, Configuration Manual

Page: 355 / 762

Configure Network Address Translation (NAT) 351
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The debugging of the network becomes even more difficult. For instance,
when one host machine of the internal network attempts to attack other
networks, it is very difficult to pinpoint which computer is attacking computer,
since the IP address of the host machine is shielded.
Performance of Network Address Translation (NAT)
When the speed of the broadband of the link is below 1Mbps, the address
translation has little impact on the performance of the network. In this case, the
bottleneck of the network transmission is on the transmission line. When the
speed is above 1Mbps, the address translation will have some impact on the
performance of the routers.
Configure NAT NAT configuration includes:
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Configure the address pool
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Configure the correlation between the access control list and address pool
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Configure the correlation between the access control list and the interface
(EASY IP)
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Configure the internal server
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Configure the valid time of address translation
1 Configure the address pool
The address pool is a pool of the consecutive IP addresses. When the internal data
packet arrives at the external network through address translation, it will select
one address from the address pool as the translated source address.
Please process the following configurations in the system view.
Table 383 Configure address pool
All the addresses in the address pool should be consecutive. For the most, 64
addresses can be defined in each address pool.
An address pool can not be deleted, if it is correlated to one access control list and
address translation has started.
2 Configure the correlation between the access control list and address pool
Multiple-to-multiple address translation can be implemented, after the access
control list and the address pool are correlated. The access control list is generated
by
rule
command. It defines some rules, according to the format of the header of
the IP data packet message and the header of data packet of the lower layer
protocol it bears, which denotes the enable or disable of the data packets with
certain features. For the data packet configured with NAT, it goes though address
analysis before the message is forwarded. For the data packet no configured with
NAT, it goes ahead with the normal forwarding process.
s according to this correlation relationship the addresses are translated. When the
data packets of the internal network are to be transmitted to the external
network: firstly, it is determined if the data packets are allowed according to the
Operation Command
Define one address pool
nat address-group start-addr
end-addr pool-name
Delete one address pool
undo nat address-group
pool-name