Zyxel NBG-419N Router Manual PDF (Setup & Configuration Guide)

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Chapter 14 DHCP Server

NBG-419N User’s Guide

126

14.4

Advanced Screen

This screen allows you to assign IP addresses on the LAN to specific individual computers based on

their MAC addresses. You can also use this screen to configure the DNS server information that the

NBG-419N sends to the DHCP clients.

To change your NBG-419N’s static DHCP settings, click

Network

>

DHCP Server

>

Advanced

.

The following screen displays.

Figure 91

Network > DHCP Server > Advanced

The following table describes the labels in this screen.

Apply

Click

Apply

to save your changes back to the NBG-419N.

Reset

Click

Reset

to begin configuring this screen afresh.

Table 55

Network > DHCP Server > General

LABEL

DESCRIPTION

Table 56

Network > DHCP Server > Advanced

LABEL

DESCRIPTION

LAN Static DHCP Table

#

This is the index number of the static IP table entry (row).

MAC Address

Type the MAC address (with colons) of a computer on your LAN.

IP Address

Type the LAN IP address of a computer on your LAN.

Page 127 / 292

Chapter 14 DHCP Server

NBG-419N User’s Guide

127

DNS Server

DNS Servers

Assigned by DHCP

Server

The NBG-419N passes a DNS (Domain Name System) server IP address (in the

order you specify here) to the DHCP clients. The NBG-419N only passes this

information to the LAN DHCP clients when you select the

Enable DHCP Server

check box. When you clear the

Enable DHCP Server

check box, DHCP service

is disabled and you must have another DHCP sever on your LAN, or else the

computers must have their DNS server addresses manually configured.

First DNS Server

Second DNS Server

Select

From ISP

if your ISP dynamically assigns DNS server information (and

the NBG-419N's WAN IP address). The field to the right displays the (read-

only) DNS server IP address that the ISP assigns.

Select

User-Defined

if you have the IP address of a DNS server. Enter the

DNS server's IP address in the field to the right. If you chose

User-Defined

,

but leave the IP address set to 0.0.0.0,

User-Defined

changes to

None

after

you click

Apply

. If you set a second choice to

User-Defined

, and enter the

same IP address, the second

User-Defined

changes to

None

after you click

Apply

.

Select

DNS Relay

to have the NBG-419N act as a DNS proxy. The NBG-419N's

LAN IP address displays in the field to the right (read-only). The NBG-419N

tells the DHCP clients on the LAN that the NBG-419N itself is the DNS server.

When a computer on the LAN sends a DNS query to the NBG-419N, the NBG-

419N forwards the query to the NBG-419N's system DNS server (configured in

the

WAN > Internet Connection

screen) and relays the response back to the

computer. You can only select

DNS Relay

for one of the three servers; if you

select

DNS Relay

for a second or third DNS server, that choice changes to

None

after you click

Apply

.

Select

None

if you do not want to configure DNS servers. If you do not

configure a DNS server, you must know the IP address of a computer in order

to access it.

Apply

Click

Apply

to save your changes back to the NBG-419N.

Reset

Click

Reset

to begin configuring this screen afresh.

Table 56

Network > DHCP Server > Advanced

LABEL

DESCRIPTION

Page 128 / 292

Chapter 14 DHCP Server

NBG-419N User’s Guide

128

Page 129 / 292

NBG-419N User’s Guide

129

C

HAPTER

15

Network Address Translation (NAT)

15.1

Overview

NAT (Network Address Translation - NAT, RFC 1631) is the translation of the IP address of a host in

a packet. For example, the source address of an outgoing packet, used within one network is

changed to a different IP address known within another network.

Each packet has two addresses – a source address and a destination address. For outgoing packets,

NAT maps private (local) IP addresses to globally unique ones required for communication with

hosts on other networks. It replaces the original IP source address in each packet and then

forwards it to the Internet. The NBG-419N keeps track of the original addresses and port numbers

so incoming reply packets can have their original values restored. The following figure illustrates

this.

Figure 92

NAT Example

For more information on IP address translation, refer to

RFC 1631

,

The IP Network Address

Translator (NAT)

.

15.2

What You Can Do

•

Use the

General

screen (

Section 15.3 on page 130

) to enable NAT and set a default server.

•

Use the

Application

screen (

Section 15.4 on page 130

) o forward incoming service requests to

the server(s) on your local network.

•

Use the

Advanced

screen (

Section 15.5 on page 132

) to change your NBG-419N’s trigger port

settings.

Page 130 / 292

Chapter 15 Network Address Translation (NAT)

NBG-419N User’s Guide

130

15.3

General NAT Screen

Use this screen to enable NAT and set a default server. Click

Network > NAT > General

to open

the following screen.

Figure 93

Network > NAT > General

The following table describes the labels in this screen.

15.4

NAT Application Screen

Use the

Application

screen to forward incoming service requests to the server(s) on your local

network. You may enter a single port number or a range of port numbers to be forwarded, and the

local IP address of the desired server. The port number identifies a service; for example, web

service is on port 80 and FTP on port 21. In some cases, such as for unknown services or where one

server can support more than one service (for example both FTP and web service), it might be

better to specify a range of port numbers.

Table 57

Network > NAT > General

LABEL

DESCRIPTION

NAT Setup

Enable Network

Address

Translation

Network Address Translation (NAT) allows the translation of an Internet protocol

address used within one network (for example a private IP address used in a

local network) to a different IP address known within another network (for

example a public IP address used on the Internet).

Select the check box to enable NAT.

Default Server Setup

Server IP

Address

In addition to the servers for specified services, NAT supports a default server. A

default server receives packets from ports that are not specified in the

Application

screen.

If you do not assign a

Default

Server

IP address

, the NBG-419N discards all

packets received for ports that are not specified in the

Application

screen or

remote management.

Apply

Click

Apply

to save your changes back to the NBG-419N.

Reset

Click

Reset

to begin configuring this screen afresh.

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