3Com REMOTE ACCESS SYSTEM 1500, Руководство по управлению

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254 C
HAPTER
16: U
SING
N
ETWORK
A
DDRESS
T
RANSLATION AND
P
ORT
A
DDRESS
T
RANSLATION
192.168.111.1), and the packet is routed to the correct user on the
private network.
■
The next user is assigned the next free IP address from the pool. For
example, 200.1.1.2. When the connection for a user ends, the IP
address is returned to the public address pool.
NAT is either “dynamic” or “static.” The preceding example is dynamic
and is depicted in the following diagram. (Figure 19 shows fewer
addresses in the pool than in the preceding example.)
Figure 19 Dynamic NAT
Public Private
200.1.1.1
200.1.1.3
200.1.1.2
Public
192.168.111.1
Private
200.1.1.1
200.1.1.3
200.1.1.2
Public
192.168.111.1
Private
200.1.1.1
192.168.111.3
200.1.1.3
200.1.1.2
Public Private
200.1.1.1
192.168.111.3
200.1.1.3
200.1.1.2
When no users are attempting
to access the public network,
no addresses are assigned.
When a user attempts to access the public
network, the private address of the user is
assigned the first available IP address in the
public IP address pool.
When another user attempts to access
the public network, the private address
of the user is assigned the next available
IP address in the public IP address pool.
W h e n a c o n n e c t i o n e n d s ,
the public IP address of
that connection again
becomes available.