Chapter 9 Network Address Translation (NAT)
IAD User’s Guide
112
9.6 NAT Technical Reference
This chapter contains more information regarding NAT.
9.6.1 NAT Definitions
Inside/outside denotes where a host is located relative to the IAD, for example,
the computers of your subscribers are the inside hosts, while the web servers on
the Internet are the outside hosts.
Global/local denotes the IP address of a host in a packet as the packet traverses a
router, for example, the local address refers to the IP address of a host when the
packet is in the local network, while the global address refers to the IP address of
the host when the same packet is traveling in the WAN side.
Note that inside/outside refers to the location of a host, while global/local refers to
the IP address of a host used in a packet. Thus, an inside local address (ILA) is the
IP address of an inside host in a packet when the packet is still in the local
network, while an inside global address (IGA) is the IP address of the same inside
host when the packet is on the WAN side. The following table summarizes this
information.
NAT never changes the IP address (either local or global) of an outside host.
9.6.2 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
Table 32
NAT Definitions
ITEM
DESCRIPTION
Inside
This refers to the host on the LAN.
Outside
This refers to the host on the WAN.
Local
This refers to the packet address (source or destination) as the packet travels
on the LAN.
Global
This refers to the packet address (source or destination) as the packet travels
on the WAN.
Summary of Contents for P-3202HN-Ba
Page 2: ......
Page 8: ...Safety Warnings IAD User s Guide 8...
Page 10: ...Contents Overview IAD User s Guide 10...
Page 18: ...Table of Contents IAD User s Guide 18...
Page 19: ...19 PART I User s Guide...
Page 20: ...20...
Page 28: ...Chapter 1 Introduction IAD User s Guide 28...
Page 39: ...39 PART II Technical Reference...
Page 40: ...40...
Page 50: ...Chapter 4 Status Screens IAD User s Guide 50...
Page 54: ...Chapter 5 Device Mode Screen IAD User s Guide 54...
Page 68: ...Chapter 7 LAN Setup IAD User s Guide 68...
Page 128: ...Chapter 10 Voice IAD User s Guide 128...
Page 158: ...Chapter 12 Firewalls IAD User s Guide 158...
Page 162: ...Chapter 13 Static Route IAD User s Guide 162...
Page 173: ...Chapter 14 Quality of Service QoS IAD User s Guide 173 Figure 81 QoS Class Example VoIP...
Page 174: ...Chapter 14 Quality of Service QoS IAD User s Guide 174 Figure 82 QoS Class Example Boss...
Page 182: ...Chapter 15 Dynamic DNS Setup IAD User s Guide 182...
Page 210: ...Chapter 17 Universal Plug and Play UPnP IAD User s Guide 210...
Page 214: ...Chapter 18 System IAD User s Guide 214...
Page 218: ...Chapter 19 Logs IAD User s Guide 218...
Page 224: ...Chapter 21 Diagnostic IAD User s Guide 224...
Page 230: ...Chapter 22 Troubleshooting IAD User s Guide 230...
Page 238: ...Chapter 23 Product Specifications IAD User s Guide 238...