Multi-Tech Systems RF500S manual NAT Technology

Glossary

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 address from your ISP (Internet Service Provider). Using a registered IP address on your Intranet or LAN 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 remainder 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 travels 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 in 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.

RouteFinder RF500S User Guide 134