Dynalink RTA1025W Chapter 6: Glossary

Chapter 6: Glossary

ARP is a TCP/IP protocol for mapping an IP address to a physical machine a ddress that is

recognized in the local net work, such as an Ethernet address.

A host wishing to obtain a physical ad dress broad casts an ARP request onto the TCP/IP network.

The host on the network that has the IP address in the request then replies with its physical

hardware address.

Inverse ARP (In-ARP), on the other hand, is used by a host to discover its IP address. In this case,

the host broadcasts its physical add ress and a RARP server replies with the host's IP addres s.

When operates as a DHCP server, the ADSL Ro uter assign IP addresses to the client PCs on the

LAN. The client PCs “leases” the se Privat e IP addresses for a use r-defined a m ount of time. After

the lease time expires, the private IP address is made available for assigning to other network

devices.

The DHCP IP address can be a single, fixed public IP address, an ISP assigned public IP address,

or a private IP address.

If you enable DHCP server on a private IP address, a public IP address will have to be assign ed

to the NAT IP address, and NAT has to be enabled so that the DHCP IP address can be

translated into a public IP addre ss. By this, the client PCs a re able to access the Internet.

A LAN is a computer network limited to the immediate area, usually the same building or floor of a

building. A WAN, on the other hand, is an outside connection to another netwo rk or the Internet.

The Ethernet side of the ADSL Router is called the LAN port. It is a twisted-pair Ethernet

10Base-T interface. A hub can be conn ected to the LAN port. More than one computers, such as

server or printer, can be connected through this hub to the ADSL Router and composes a LAN.

The DSL port of the ADSL Router composes the WAN interface, which supports PPP or RFC

1483 connecting to another remote DS L device.

NAT is an Internet standard that transl ates a p rivate IP within one network to a public IP address,

either a static or dynamic one. NAT provides a type of firewall by hiding internal IP addresses. It

also enables a com pany to use more internal IP addresses.

If the IP addresses given by your ISP are not enough for ea ch PC on the LAN and the ADSL

Router, you need to use NAT. With NAT, you make up a private IP network for the LAN and

assign an IP address from that netwo rk to each PC. One of some public addresses is config ured

and mapped to a private workstation address when accesses are made through the gateway to a

public network.

For example, the ADSL Router is assign ed with the public IP add ress of 168.111.2.1. With NAT

enabled, it creates a Virtual LAN. Each PC on the Virtual LAN is assigned with a private IP

address with default value of 192.168.2.2 to 192.168.2.254. These PCs are not accessible by the

outside world but they can communicate with the outside world through the public IP 168.111.2.1.

Private IP addresses are also LAN IP addresses, but are considered “illegal” IP addresses to the

Internet. They are private to an enterprise while still permitting full network layer connectivity

between all hosts inside an enterprise as well as all public hosts of different enterprises.