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VSG-1200 User’s Guide
66
Chapter 5 NAT Pool
5.1.2 What NAT Does
In the simplest form, NAT changes the source IP address in a packet received from a
subscriber (the inside local address) to another (the inside global address) before forwarding
the packet to the WAN side. When the response comes back, NAT translates the destination
address (the inside 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 VSG 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)
.
5.1.3 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 VSG keeps track of the original addresses and port numbers so
incoming reply packets can have their original values restored.
5.2 VPN and NAT
A VPN (Virtual Private Network) provides secure communications between sites without the
expense of leased site-to-site lines. A secure VPN is a combination of tunneling, encryption,
authentication, access control and auditing technologies/services used to transport traffic over
the Internet or any insecure network that uses the TCP/IP protocol suite for communication.
The VSG allows subscribers to create a VPN tunnel to a remote site.
By default, the VSG performs NAT on the LAN; mapping multiple private LAN addresses to
a single public address on the WAN. This prevents subscribers from creating multiple VPN
connections to a remote VPN device that allows only one VPN connection per source IP
address.
Note:
For IPSec, the VSG does not support AH protocol.
Содержание VSG-1200
Страница 1: ...VSG 1200 Vantage Service Gateway User s Guide Version 1 08 1 2006 ...
Страница 8: ...VSG 1200 User s Guide 8 Customer Support ...
Страница 22: ...VSG 1200 User s Guide 22 List of Figures ...
Страница 26: ...VSG 1200 User s Guide 26 List of Tables ...
Страница 40: ...VSG 1200 User s Guide 40 Chapter 2 Hardware Installation and Connection ...
Страница 45: ...VSG 1200 User s Guide Chapter 3 The Web Configurator 45 Figure 13 System Setting System ...
Страница 52: ...VSG 1200 User s Guide 52 Chapter 3 The Web Configurator ...
Страница 64: ...VSG 1200 User s Guide 64 Chapter 4 LAN WAN and Server Setup ...
Страница 74: ...VSG 1200 User s Guide 74 Chapter 6 Authentication Figure 29 System Setting Authentication ...
Страница 102: ...VSG 1200 User s Guide 102 Chapter 9 Dynamic Subscriber Accounts ...
Страница 128: ...VSG 1200 User s Guide 128 Chapter 13 Subscriber Information Window ...
Страница 130: ...VSG 1200 User s Guide 130 Chapter 14 Account Printout Figure 79 Customization Account Printout ...
Страница 133: ...VSG 1200 User s Guide Chapter 14 Account Printout 133 Figure 82 Static Account Printout Statement Printer Example ...
Страница 135: ...VSG 1200 User s Guide Chapter 14 Account Printout 135 Figure 85 Dynamic Account Printout Statement Printer Example ...
Страница 136: ...VSG 1200 User s Guide 136 Chapter 14 Account Printout ...
Страница 140: ...VSG 1200 User s Guide 140 Chapter 15 User Agreement Page ...
Страница 144: ...VSG 1200 User s Guide 144 Chapter 16 Bandwidth Management ...
Страница 158: ...VSG 1200 User s Guide 158 Chapter 19 LAN Devices ...
Страница 162: ...VSG 1200 User s Guide 162 Chapter 20 Static Route ...
Страница 170: ...VSG 1200 User s Guide 170 Chapter 21 Syslog and Session Trace ...
Страница 174: ...VSG 1200 User s Guide 174 Chapter 22 SNMP ...
Страница 198: ...VSG 1200 User s Guide 198 Chapter 25 Secure Socket Layer ...
Страница 206: ...VSG 1200 User s Guide 206 Chapter 26 The SMT ...
Страница 214: ...VSG 1200 User s Guide 214 Chapter 27 LAN and WAN Setup Using the SMT ...
Страница 226: ...VSG 1200 User s Guide 226 Chapter 28 Configuration and Firmware Maintenance ...
Страница 236: ...VSG 1200 User s Guide 236 Appendix B IP Address Assignment Conflicts ...
Страница 238: ...VSG 1200 User s Guide 238 Appendix C Subscriber Login ...
Страница 242: ...VSG 1200 User s Guide 242 Appendix D Vendor Specific Attributes ...
Страница 252: ...VSG 1200 User s Guide 252 Appendix F Cable Types and Cable Pin Assignments ...
Страница 264: ...VSG 1200 User s Guide 264 Appendix G Setting up Your Computer s IP Address ...
Страница 272: ...VSG 1200 User s Guide 272 Appendix H IP Subnetting ...