User's Guide

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Table Of Contents

Contents Overview
Table of Contents
Introduction
- 1.1 Overview
- 1.2 Applications
- 1.3 Ways to Manage the EMG1302-R10A
- 1.4 Good Habits for Managing the EMG1302-R10A
- 1.5 LEDs
- 1.6 The WPS Button
- 1.7 Wall Mounting
Introducing the Web Configurator
- 2.1 Overview
- 2.2 Login Accounts
- 2.3 Accessing the Web Configurator
- 2.4 Resetting the EMG1302-R10A
  - 2.4.1 Procedure to Use the RESET Button
Quick Start
- 3.1 Overview
- 3.2 Quick Start Setup
Monitor
- 4.1 Overview
- 4.2 What You Can Do
- 4.3 The Log Screen
  - 4.3.1 View Log
  - 4.3.2 Log Setting
- 4.4 DHCP Table
- 4.5 Packet Statistics
- 4.6 WLAN Station Status
Router Mode
- 5.1 Overview
- 5.2 Router Mode Status Screen
  - 5.2.1 Navigation Panel
Tutorials
- 6.1 Overview
- 6.2 Set Up a Wireless Network with WPS
  - 6.2.1 Push Button Configuration (PBC)
  - 6.2.2 PIN Configuration
- 6.3 Configure Wireless Security without WPS
  - 6.3.1 Configure Your Notebook
- 6.4 Using Multiple SSIDs on the EMG1302-R10A
  - 6.4.1 Configuring Security Settings of Multiple SSIDs
WAN
- 7.1 Overview
- 7.2 What You Can Do
- 7.3 What You Need To Know
  - 7.3.1 Configuring Your Internet Connection
  - 7.3.2 Multicast
- 7.4 Management WAN
  - 7.4.1 Add/Edit Internet Connection
  - 7.4.2 Bridge Encapsulation
- 7.5 Advanced WAN Screen
- 7.6 IPv6 Screen
Wireless LAN
- 8.1 Overview
- 8.2 What You Can Do
- 8.3 What You Should Know
- 8.4 General Wireless LAN Screen
- 8.5 Wireless Security
  - 8.5.1 No Security
  - 8.5.2 WPA2-PSK
- 8.6 More AP
  - 8.6.1 More AP Edit
- 8.7 MAC Filter
- 8.8 Wireless LAN Advanced Screen
- 8.9 Quality of Service (QoS) Screen
- 8.10 WPS Screen
- 8.11 WPS Station Screen
- 8.12 Scheduling Screen
- 8.13 WDS
LAN
- 9.1 Overview
- 9.2 What You Can Do
- 9.3 What You Need To Know
  - 9.3.1 IP Pool Setup
  - 9.3.2 LAN TCP/IP
- 9.4 LAN IP Screen
DHCP Server
- 10.1 Overview
- 10.2 What You Can Do
- 10.3 What You Need To Know
- 10.4 The DHCP General Screen
- 10.5 The DHCP Advanced Screen
- 10.6 The DHCP Client List Screen
Quality of Service (QoS)
- 11.1 Overview
  - 11.1.1 What You Can Do in the QoS Screens
  - 11.1.2 What You Need to Know About QoS
- 11.2 The Quality of Service General Screen
- 11.3 The Rule-based QoS Screen
  - 11.3.1 Adding a Rule
- 11.4 QoS Technical Reference
NAT
- 12.1 Overview
- 12.2 What You Can Do
- 12.3 What You Need To Know
- 12.4 The NAT General Screen
- 12.5 The NAT Port Forwarding Screen
- 12.6 The NAT Trigger Port Screen
- 12.7 The ALG Screen
DDNS
- 13.1 Overview
- 13.2 The DDNS General Screen
Routing
- 14.1 Overview
- 14.2 Static Route Screen
  - 14.2.1 Add/Edit Static Route Screen
- 14.3 The Dynamic Routing Screen
Interface Group
- 15.1 Overview
- 15.2 The Interface Group Screen
  - 15.2.1 Add Interface Group
Security
- 16.1 Overview
- 16.2 What You Can Do
- 16.3 What You Need To Know
- 16.4 The Firewall General Screen
- 16.5 The Firewall Services Screen
Content Filtering
- 17.1 Overview
- 17.2 What You Need To Know
- 17.3 Content Filter
IPv6 Firewall
- 18.1 Overview
- 18.2 The IPv6 Firewall Screen
Remote Management
- 19.1 Overview
- 19.2 What You Need to Know
  - 19.2.1 Remote Management and NAT
- 19.3 What You Can Do
- 19.4 The WWW Screen
- 19.5 The Telnet Screen
- 19.6 The SNMP Screen
- 19.7 The TR069 Screen
Universal Plug-and-Play (UPnP)
- 20.1 Overview
- 20.2 What You Need to Know
  - 20.2.1 NAT Traversal
  - 20.2.2 Cautions with UPnP
- 20.3 UPnP Screen
- 20.4 Technical Reference
  - 20.4.1 Using UPnP in Windows XP Example
  - 20.4.2 Web Configurator Easy Access
Maintenance
- 21.1 Overview
- 21.2 What You Can Do
- 21.3 General Screen
- 21.4 Account Screen
  - 21.4.1 Account Setup Screen
- 21.5 Time Setting Screen
- 21.6 Firmware Upgrade Screen
- 21.7 Configuration Backup/Restore Screen
- 21.8 Restart Screen
Troubleshooting
- 22.1 Overview
- 22.2 Power, Hardware Connections, and LEDs
- 22.3 EMG1302-R10A Access and Login
- 22.4 Internet Access
- 22.5 Resetting the EMG1302-R10A to Its Factory Defaults
- 22.6 Wireless Router/AP Troubleshooting
Customer Support
Pop-up Windows, JavaScript and Java Permissions
Wireless LANs
Common Services
Legal Information
Index

Chapter 12 NAT

EMG1302-R10A User’s Guide

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global address) back to the inside local address before forwarding it to the original inside host. Note

that the IP address (either local or global) of an outside host is never changed.

The global IP addresses for the inside hosts can be either static or dynamically assigned by the ISP.

In addition, you can designate servers, for example, a web server and a telnet server, on your local

network and make them accessible to the outside world. If you do not define any servers, NAT

offers the additional benefit of firewall protection. With no servers defined, your EMG1302-R10A

filters out all incoming inquiries, thus preventing intruders from probing your network. For more

information on IP address translation, refer to RFC 1631, The IP Network Address Translator (NAT).

How NAT Works

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

the ILA (Inside Local Address) is the source address on the LAN, and the IGA (Inside Global

Address) is the source address on the WAN. For incoming packets, the ILA is the destination

address on the LAN, and the IGA is the destination address on the WAN. 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

EMG1302-R10A 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 59 How NAT Works