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5. Configuring the FrameSaver DSL Router
5-8
December 2002 9700-A2-GB20-20
Network Address Port Translation
Network Address Port Translation (NAPT) allows multiple clients in a local network
to simultaneously access remote networks using a single IP address. This benefits
telecommuters and SOHO (Small Office/Home Office) users that have multiple
clients in an office running TCP/UDP applications. NAPT is sometimes referred to
as PAT (Port Address Translation).
NAPT provides a many-to-one mapping and uses one public address to interface
numerous private users to an external network. All hosts on the global side view all
hosts on the local side as one Internet host. The local hosts continue to use their
corporate or private addresses. When the hosts are communicating with each
other, the translation is based on the IP address and the IP port numbers used by
TCP/IP applications. Only TCP/UDP applications can access the public network.
NAPT Configuration Example
In this NAPT example the router is configured for NAPT using:
A single public IP address. Multiple public addresses can be used.
A public network. NAPT can also be used between private networks.
An access list. A pool can also be used, instead or in addition.
NAPT Mapping Public IP Address Private IP Addresses
172.20.95.2:zzzz 10.1.3.2:zzzz
172.20.95.2:yyyy 10.1.3.3:yyyy
172.20.95.2:xxxx 10.1.3.4:xxxx
NAPT Example
01-16947
10.1.3.1 Public
Network
Public IP
Address
Ethernet
Private
Network
FrameSaver
xDSL
Router