Glossary
RouteFinder RF500S User Guide 134
N
NAT Technology
NAT is short for Network Address Translation. NAT is an Internet standard that enables a
local-area network to use one set of IP addresses for internal traffic and a second set of IP
addresses for external traffic. The RF500S provides the necessary IP address translations.
NAT is sometimes referred to as “IP Address Masquerading”. This technology provides a
type of firewall by hiding the internal IP addresses.
How does it work?
Every IP address on the Internet is a Registered or legal IP address. Therefore, no two IP
addresses on the Internet are the same. For you to use your network device to access the
Internet you need a registered IP ad dress from your ISP (Internet Service Provider). Using
a registered IP address on your Intranet or LA N is not necessary. When clients on your
network start surfing the Internet, your RouteFinder will receive all the requests for
information. The RouteFinder will dial-up your ISP and your ISP will give your RouteFinder
a registered legal IP address. Your RouteFinder uses this IP address to request information
saying ,”send all information back to me at this IP address”. In essence it appears as
though all your clients requests are coming from that one IP address (hence the name IP
masquerading). When all the information comes back through the RouteFinder, it sorts the
data using an Address Translation Table and returns the data to the computer on your
network that requested it.
If someone on the Internet tries to access your network, the RouteFinder’s firewall
function stops the request. The device will not reverse translate network addresses unless
you have specifically allowed this feature using the Virtual Server function (IP Mapping).
Network Address
The network portion of an IP address. For a class A network, the network address is the
first byte of the IP address. For a class B network, the network address is the first two
bytes of the IP address. For a class C network, the network address is the first three bytes
of the IP address. In each case, the r emainder is the host address. In the Internet,
assigned network addresses are globally unique.
P
Packet
A packet is a piece of a message transmitted over a packet-switching network. A packet
contains the destination address of the message as well as the data. In IP networks,
packets are often called datagrams.
Port Number
The term port can mean the connector on your computer or it can be thought of as a
server number. Every service that t ravels over phone lines and modems has a standard
port number. For example, the World Wide Web service uses the standard port number,
80 and the standard telnet port is 23.
Port numbers are controlled and assigned by the IANA (Internet Assigned Numbers
Authority). Most computers have a table i n their systems containing a list of ports that
have been assigned to specific services. You can also find lists of standard port numbers
on the World Wide Web.
Protocol
A formal description of message formats and the rules two computers must follow to
exchange those messages. You can think of protocols like languages. If two computers
or devices aren’t speaking the same language to each other, they won’t be able to
communicate.