Samsung Ubigate iBG3026 Configuration Manual page 279

Ubigate iBG3026 Configuration Guide/Ed.00
The Ubigate iBG3026 also adds an entry into a table it keeps, which maps the
internal address and source port number that the PC generated against the port
number it allocated to this session. Therefore, when some.server.com sends a
reply packet to the PC, the Ubigate iBG3026 can quickly determine how it
needs to re-write the packet before transmitting it back on to the LAN.
Dynamic NAT is used when packets destined for the Internet are transported
from a LAN using the public source IP address assigned to the local router.
Dynamic NAT performs this task well, but it does not permit providing
services to the Internet from inside a LAN which requires the use of static
NAT. Static NAT also requires a public address from the upstream service
provider. Individual PCs within a LAN are assigned RFC 1918 reserved IP
addresses to enable access to other PCs within the LAN. The Ubigate
iBG3026 is configured with static mapping, which maps the internal RFC
1918 IP addresses for each PC to the appropriate public IP address. When
traffic is sent to the public address listed in the static mapping, the Ubigate
iBG3026 forwards the packets to the correct PC within the LAN, according to
the mapping relationship established.
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