ZyWALL 2 Plus User’s Guide
411
C
H A P T E R
24
ALG Screen
This chapter covers how to use the ZyWALL’s ALG feature to allow certain applications to
pass through the ZyWALL.
24.1 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.
24.1.1 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
.
24.1.2 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 ADSL 2+ Security Gateway
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Страница 25: ...Table of Contents ZyWALL 2 Plus User s Guide 25 Index 679 ...
Страница 26: ...Table of Contents ZyWALL 2 Plus User s Guide 26 ...
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Страница 88: ...Chapter 3 Wizard Setup ZyWALL 2 Plus User s Guide 88 ...
Страница 131: ...131 PART II Network LAN Screens 133 Bridge Screens 145 WAN Screens 151 DMZ Screens 171 Wireless LAN 181 ...
Страница 132: ...132 ...
Страница 144: ...Chapter 6 LAN Screens ZyWALL 2 Plus User s Guide 144 ...
Страница 180: ...Chapter 9 DMZ Screens ZyWALL 2 Plus User s Guide 180 ...
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Страница 209: ...Chapter 11 Firewall ZyWALL 2 Plus User s Guide 209 Figure 138 SECURITY FIREWALL Rule Summary Edit ...
Страница 221: ...Chapter 11 Firewall ZyWALL 2 Plus User s Guide 221 Figure 149 My Service Firewall Rule Example Rule Summary Completed ...
Страница 222: ...Chapter 11 Firewall ZyWALL 2 Plus User s Guide 222 ...
Страница 252: ...Chapter 13 Content Filtering Reports ZyWALL 2 Plus User s Guide 252 ...
Страница 265: ...Chapter 14 IPSec VPN ZyWALL 2 Plus User s Guide 265 Figure 178 SECURITY VPN VPN Rules IKE Edit Gateway Policy ...
Страница 274: ...Chapter 14 IPSec VPN ZyWALL 2 Plus User s Guide 274 Figure 181 SECURITY VPN VPN Rules IKE Edit Network Policy ...
Страница 306: ...Chapter 15 Certificates ZyWALL 2 Plus User s Guide 306 Figure 203 SECURITY CERTIFICATES My Certificates Create Basic ...
Страница 328: ...Chapter 16 Authentication Server ZyWALL 2 Plus User s Guide 328 ...
Страница 330: ...330 ...
Страница 346: ...Chapter 17 Network Address Translation NAT ZyWALL 2 Plus User s Guide 346 ...
Страница 350: ...Chapter 18 Static Route ZyWALL 2 Plus User s Guide 350 ...
Страница 398: ...Chapter 21 Remote Management ZyWALL 2 Plus User s Guide 398 ...
Страница 416: ...Chapter 24 ALG Screen ZyWALL 2 Plus User s Guide 416 ...
Страница 417: ...417 PART V Logs and Maintenance Logs Screens 419 Maintenance 447 ...
Страница 418: ...418 ...
Страница 423: ...Chapter 25 Logs Screens ZyWALL 2 Plus User s Guide 423 Figure 274 LOGS Log Settings ...
Страница 466: ...466 ...
Страница 474: ...Chapter 27 Introducing the SMT ZyWALL 2 Plus User s Guide 474 ...
Страница 496: ...Chapter 30 LAN Setup ZyWALL 2 Plus User s Guide 496 ...
Страница 504: ...Chapter 32 DMZ Setup ZyWALL 2 Plus User s Guide 504 ...
Страница 508: ...Chapter 33 Wireless Setup ZyWALL 2 Plus User s Guide 508 ...
Страница 556: ...Chapter 38 Filter Configuration ZyWALL 2 Plus User s Guide 556 ...
Страница 570: ...Chapter 40 System Information Diagnosis ZyWALL 2 Plus User s Guide 570 ...
Страница 586: ...Chapter 41 Firmware and Configuration File Maintenance ZyWALL 2 Plus User s Guide 586 ...
Страница 594: ...Chapter 42 System Maintenance Menus 8 to 10 ZyWALL 2 Plus User s Guide 594 ...
Страница 598: ...Chapter 43 Remote Management ZyWALL 2 Plus User s Guide 598 ...
Страница 603: ...603 PART VII Troubleshooting and Specifications Troubleshooting 605 Product Specifications 613 ...
Страница 604: ...604 ...
Страница 612: ...Chapter 45 Troubleshooting ZyWALL 2 Plus User s Guide 612 ...
Страница 620: ...620 ...
Страница 644: ...Appendix B Pop up Windows JavaScripts and Java Permissions ZyWALL 2 Plus User s Guide 644 ...
Страница 668: ...Appendix E Importing Certificates ZyWALL 2 Plus User s Guide 668 ...
Страница 672: ...Appendix F Legal Information ZyWALL 2 Plus User s Guide 672 ...
Страница 678: ...Appendix G Customer Support ZyWALL 2 Plus User s Guide 678 ...