User's Manual

Part # 34357-MNL Rev.03 SPEEDLAN 9200 User Guide
5-10
IP addresses. This enables companies to communicate with other devices on the
Internet with a single global IP address (or more than one IP address).
For example, a company can provide its clients with one IP address, allowing access to
the company's firewall only. This IP address is not a "real" address on the company's
internal network, but it is successfully translated to the correct IP location through NAT
(i.e., NAT router). Therefore, the company controls access through firewalls and
provides multiple IP addresses to outside customers without excessive limited resources,
or "global" Internet IP protocols.
NAPT
What differentiates NAPT from NAT? NAPT (or Network Address Port Translation) not
only translates the IP address but also the transport layer port. Thus, if an inbound
packet was addressed to a web server port on 80, the NAPT device would translate and
pass to the packet to the private network's web server. Without port translation, the NAT
device has no means of knowing which host in the private network can pass packets to
other devices. For an example see, Diagram of Incoming NAT, page 5-12.