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Chapter 11 Network Address Translation (NAT)
P-2601HN(L)-F1 Series User’s Guide
155
NAT never changes the IP address (either local or global) of an outside host.
11.4.2 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 ZyXEL Device 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).
11.4.3 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 (and TCP or UDP source port numbers for
Many-to-One and Many-to-Many Overload NAT mapping) in each packet and then
forwards it to the Internet. The ZyXEL Device keeps track of the original addresses
Содержание P-2601HN(L)-F1 Series
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Страница 8: ...Safety Warnings P 2601HN L F1 Series User s Guide 8 ...
Страница 10: ...Contents Overview P 2601HN L F1 Series User s Guide 10 ...
Страница 19: ...19 PART I User s Guide ...
Страница 20: ...20 ...
Страница 59: ...59 PART II Technical Reference ...
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Страница 110: ...Chapter 6 Wireless P 2601HN L F1 Series User s Guide 110 ...
Страница 130: ...Chapter 8 Routing P 2601HN L F1 Series User s Guide 130 ...
Страница 134: ...Chapter 9 DNS Route P 2601HN L F1 Series User s Guide 134 ...
Страница 178: ...Chapter 16 VoIP P 2601HN L F1 Series User s Guide 178 Figure 81 VoIP SIP SIP Service Provider ...
Страница 202: ...Chapter 16 VoIP P 2601HN L F1 Series User s Guide 202 ...
Страница 206: ...Chapter 17 Logs P 2601HN L F1 Series User s Guide 206 ...
Страница 212: ...Chapter 18 System Monitor P 2601HN L F1 Series User s Guide 212 ...
Страница 220: ...Chapter 21 SNMP P 2601HN L F1 Series User s Guide 220 ...
Страница 232: ...Chapter 26 Backup Restore P 2601HN L F1 Series User s Guide 232 ...
Страница 290: ...Appendix B Setting Up Your Computer s IP Address P 2601HN L F1 Series User s Guide 290 ...
Страница 298: ...Appendix C Pop up Windows JavaScript and Java Permissions P 2601HN L F1 Series User s Guide 298 ...
Страница 322: ...Appendix D Wireless LANs P 2601HN L F1 Series User s Guide 322 ...
Страница 332: ...Appendix F Open Software Announcements P 2601HN L F1 Series User s Guide 332 ...
Страница 344: ...Index P 2601HN L F1 Series User s Guide 344 ...