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ZyWALL 2WG User’s Guide
473
C
H A P T E R
25
ALG Screen
This chapter covers how to use the ZyWALL’s ALG feature to allow certain applications to
pass through the ZyWALL.
25.1 ALG Introduction
An Application Layer Gateway (ALG) manages a specific protocol (such as SIP, H.323 or
FTP) at the application layer. The ZyWALL can function as an ALG to allow certain NAT un-
friendly applications (such as SIP) to operate properly through the ZyWALL.
Some applications cannot operate through NAT (are NAT un-friendly) because they embed IP
addresses and port numbers in their packets’ data payload. The ZyWALL examines and uses
IP address and port number information embedded in the data stream. When a device behind
the ZyWALL uses an application for which the ZyWALL has ALG service enabled, the
ZyWALL translates the device’s private IP address inside the data stream to a public IP
address. It also records session port numbers and dynamically creates implicit NAT port
forwarding and firewall rules for the application’s traffic to come in from the WAN to the
LAN.
25.1.1 ALG and NAT
The ZyWALL dynamically creates an implicit NAT session for the application’s traffic from
the WAN to the LAN.
The ALG on the ZyWALL supports all NAT mapping types, including
One to One
,
Many to
One
,
Many to Many Overload
and
Many One to One
.
25.1.2 ALG and the Firewall
The ZyWALL uses the dynamic port that the session uses for data transfer in creating an
implicit temporary firewall rule for the session’s traffic. The firewall rule only allows the
session’s traffic to go through in the direction that the ZyWALL determines from its
inspection of the data payload of the application’s packets. The firewall rule is automatically
deleted after the application’s traffic has gone through.
Содержание ZYWALL 2 WG
Страница 1: ...www zyxel com ZyWALL 2WG Internet Security Appliance User s Guide Version 4 03 12 2007 Edition 1 ...
Страница 2: ......
Страница 8: ...Safety Warnings ZyWALL 2WG User s Guide 8 ...
Страница 42: ...List of Figures ZyWALL 2WG User s Guide 42 ...
Страница 50: ...List of Tables ZyWALL 2WG User s Guide 50 ...
Страница 52: ...52 ...
Страница 80: ...Chapter 2 Introducing the Web Configurator ZyWALL 2WG User s Guide 80 ...
Страница 100: ...Chapter 3 Wizard Setup ZyWALL 2WG User s Guide 100 ...
Страница 140: ...Chapter 4 Tutorial ZyWALL 2WG User s Guide 140 ...
Страница 145: ...145 PART II Network and Wireless LAN Screens 147 Bridge Screens 159 WAN Screens 165 DMZ Screens 201 Wireless LAN 211 ...
Страница 146: ...146 ...
Страница 158: ...Chapter 6 LAN Screens ZyWALL 2WG User s Guide 158 ...
Страница 171: ...Chapter 8 WAN Screens ZyWALL 2WG User s Guide 171 Figure 108 NETWORK WAN General ...
Страница 200: ...Chapter 8 WAN Screens ZyWALL 2WG User s Guide 200 ...
Страница 238: ...238 ...
Страница 258: ...Chapter 11 Firewall ZyWALL 2WG User s Guide 258 Figure 159 SECURITY FIREWALL Rule Summary Edit ...
Страница 270: ...Chapter 11 Firewall ZyWALL 2WG User s Guide 270 Figure 170 My Service Firewall Rule Example Rule Summary Completed ...
Страница 300: ...Chapter 13 Content Filtering Reports ZyWALL 2WG User s Guide 300 ...
Страница 313: ...Chapter 14 IPSec VPN ZyWALL 2WG User s Guide 313 Figure 199 SECURITY VPN VPN Rules IKE Edit Gateway Policy ...
Страница 322: ...Chapter 14 IPSec VPN ZyWALL 2WG User s Guide 322 Figure 202 SECURITY VPN VPN Rules IKE Edit Network Policy ...
Страница 348: ...Chapter 14 IPSec VPN ZyWALL 2WG User s Guide 348 ...
Страница 360: ...Chapter 15 Certificates ZyWALL 2WG User s Guide 360 Figure 229 SECURITY CERTIFICATES My Certificates Create Basic ...
Страница 378: ...Chapter 15 Certificates ZyWALL 2WG User s Guide 378 ...
Страница 380: ...Chapter 16 Authentication Server ZyWALL 2WG User s Guide 380 Figure 239 SECURITY AUTH SERVER Local User Database ...
Страница 384: ...384 ...
Страница 426: ...Chapter 20 Bandwidth Management ZyWALL 2WG User s Guide 426 ...
Страница 479: ...479 PART V Logs and Maintenance Logs Screens 481 Maintenance 511 ...
Страница 480: ...480 ...
Страница 485: ...Chapter 26 Logs Screens ZyWALL 2WG User s Guide 485 Figure 304 LOGS Log Settings ...
Страница 510: ...Chapter 26 Logs Screens ZyWALL 2WG User s Guide 510 ...
Страница 530: ...530 ...
Страница 558: ...Chapter 30 WAN and Dial Backup Setup ZyWALL 2WG User s Guide 558 ...
Страница 564: ...Chapter 31 LAN Setup ZyWALL 2WG User s Guide 564 ...
Страница 570: ...Chapter 32 Internet Access ZyWALL 2WG User s Guide 570 ...
Страница 574: ...Chapter 33 DMZ Setup ZyWALL 2WG User s Guide 574 ...
Страница 578: ...Chapter 34 Route Setup ZyWALL 2WG User s Guide 578 ...
Страница 582: ...Chapter 35 Wireless Setup ZyWALL 2WG User s Guide 582 ...
Страница 594: ...Chapter 37 IP Static Route Setup ZyWALL 2WG User s Guide 594 ...
Страница 614: ...Chapter 38 Network Address Translation NAT ZyWALL 2WG User s Guide 614 ...
Страница 632: ...Chapter 40 Filter Configuration ZyWALL 2WG User s Guide 632 ...
Страница 668: ...Chapter 44 System Maintenance Menus 8 to 10 ZyWALL 2WG User s Guide 668 ...
Страница 672: ...Chapter 45 Remote Management ZyWALL 2WG User s Guide 672 ...
Страница 680: ...Chapter 46 IP Policy Routing ZyWALL 2WG User s Guide 680 ...
Страница 685: ...685 PART VII Troubleshooting and Specifications Troubleshooting 687 Product Specifications 693 ...
Страница 686: ...686 ...
Страница 692: ...Chapter 48 Troubleshooting ZyWALL 2WG User s Guide 692 ...
Страница 702: ...Chapter 49 Product Specifications ZyWALL 2WG User s Guide 702 ...
Страница 704: ...704 ...
Страница 712: ...Appendix A Pop up Windows JavaScripts and Java Permissions ZyWALL 2WG User s Guide 712 ...
Страница 740: ...Appendix D Common Services ZyWALL 2WG User s Guide 740 ...
Страница 768: ...Appendix G Legal Information ZyWALL 2WG User s Guide 768 ...
Страница 774: ...Appendix H Customer Support ZyWALL 2WG User s Guide 774 ...