171.69.68.10:2031
171.69.68.10:1506
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10.6.1.2:2031
10.6.1.6:1506
10.6.1.6:131
10.6.1.2
10.6.1.6
SA
10.6.1.6:1506
SA
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My Network Internet
SA
171.69.68.10:2031
SA
171.69.68.10:1506
Inside Global
IPv4 Address
Inside Local
IPv4 Address
NAT Table
Internet to
Intranet
PAT
Scaling the Network with NAT and PAT 253
?– PAT attempts to preserve the original source port. If the source port is already
allocated, PAT attempts to ?¬?nd the ?¬?rst available port number. It starts from the
beginning of the appropriate port group, 0 to 511, 512 to 1023, or 1024 to 65535. If
PAT does not ?¬?nd an available port from the appropriate port group and if more than
one external IPv4 address is con?¬?gured, PAT moves to the next IPv4 address and tries
to allocate the original source port again. PAT continues trying to allocate the original
source port until it runs out of available ports and external IPv4 addresses.
Translating Inside Source Addresses
You can translate your own IPv4 addresses into globally unique IPv4 addresses when
you are communicating outside your network. You can con?¬?gure static or dynamic inside
source translation.
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