3Com 3C421600A, Management Manual

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256 C
HAPTER
16: U
SING
N
ETWORK
A
DDRESS
T
RANSLATION AND
P
ORT
A
DDRESS
T
RANSLATION
PAT is either “dynamic” or “static.” The preceding example is dynamic
and is depicted in the following diagram. (Figure 21 shows fewer
addresses in the pool than in the preceding example.)
Figure 21 Dynamic PAT
Figure 22 depicts static PAT.
Figure 22 Static PAT
Public
192.168.111.1, 4444
Private
200.1.1.1, 5001
200.1.1.1, 5003
200.1.1.1, 5002
When no users are attempting to
access the public network, no
addresses or ports are assigned.
When a user attempts to access the public
network, the private address and port of the
user are assigned the first available IP address
and port in the public IP address pool.
When another user attempts to access the
public network, the private address and port of
the user are assigned the next available IP
address and port in the public IP address pool.
When a connection ends,
the public IP address and
port of that connection
again become available.
Public
192.168.111.1, 4444
Private
200.1.1.1, 5001
200.1.1.1, 5003
200.1.1.1, 5002 192.168.111.3, 4444
Public Private
200.1.1.1, 5001
200.1.1.1, 5003
200.1.1.1, 5002 192.168.111.3, 4444
Public Private
200.1.1.1, 5001
200.1.1.1, 5003
200.1.1.1, 5002
Public
192.168.111.1, 4444
Private
200.1.1.1, 5001
192.168.111.4, 4444
192.168.111.3, 4444
192.168.111.2, 4444
200.1.1.1, 5004
200.1.1.1, 5003
200.1.1.1, 5002
When a user attempts to access the public
network, the private address and port of
the user are assigned the public IP
address and port defined in the table.