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What NAT Does, How NAT Works, Prestige 314 PLUS Broadband Sharing Gateway with 4-Port Switch, outside

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Prestige 314 PLUS Broadband Sharing Gateway with 4-Port Switch NAT never changes the IP address (either local or global) of an outside host. 4.1.2 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 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, e.g., 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 (for Many-to-One and Many-to-Many Overload mapping - see Table 4-2), NAT offers the additional benefit of firewall protection. If no server is defined in these cases, all incoming inquiries will be filtered out by your Prestige, thus preventing intruders from probing your network. For more information on IP address translation, refer to RFC 1631, The IP Network Address Translator (NAT). 4.1.3 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 (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 Prestige keeps track of the original addresses and port numbers so incoming reply packets can have their original values restored. The following figure illustrates this. 4-2 NAT

Section	Page
Copyright	2
Federal Communications Commission (FCC) Interference Statement	3
Information for Canadian Users	4
ZyXEL Limited Warranty	6
Customer Support	7
List of Figures	12
List of Diagrams	16
List of Charts	16
List of Tables	17
Preface	19
Getting to Know Your Prestige 314 PLUS	23
The Prestige Broadband Sharing Gateway With 4-Port Switch	23
Features of the Prestige 314 PLUS	23
Broadband Internet Access via Cable or DSL Modem	26
Internet Access Configuration Checklist	26
Hardware Installation & Initial Setup	29
Front Panel LEDs	29
Prestige Rear Panel and Connections	30
Connecting Your Prestige	31
Additional Installation Requirements	32
Turning on Your Prestige	33
Initial Screen	33
Entering the Password	33
Navigating the SMT Interface	34
Main Menu	35
System Management Terminal Interface Summary	35
Changing the System Password	36
Resetting the Prestige	37
General Setup	37
Dynamic DNS	38
Procedure For Configuring Menu 1	38
Configuring Dynamic DNS	39
WAN Setup	42
LAN Setup	43
LAN Port Filter Setup	43
Internet Access	45
TCP/IP and DHCP for LAN	45
Factory LAN Defaults	45
DHCP Configuration	45
IP Address and Subnet Mask	46
Private IP Addresses	47
RIP Setup	48
IP Multicast	48
IP Alias	49
TCP/IP and DHCP Ethernet Setup	50
IP Alias Setup	52
Internet Access Setup	54
Ethernet Encapsulation	54
PPTP Encapsulation	55
Configure PPTP Client	56
PPPoE Encapsulation	57
Internet Test Setup	58
Basic Setup Complete	59
Network Address Translation (NAT)	63
Introduction	63
NAT Definitions	63
What NAT Does	64
How NAT Works	64
NAT Application	65
NAT Mapping Types	66
Using NAT	68
SUA (Single User Account) Versus NAT	68
Applying NAT	68
NAT Setup	70
Address Mapping Sets	70
Port Forwarding Setup	75
Trigger Port Setup	78
General NAT Examples	80
Internet Access Only	80
Example 2: Internet Access with an Inside Server	82
Example 3: Multiple Public IP Addresses With Inside Servers	82
Example 4: NAT Unfriendly Application Programs	86
Remote Node Setup	89
Remote Node Profile	89
Ethernet Encapsulation	89
PPTP Encapsulation	91
PPPoE Encapsulation	93
Editing TCP/IP Options (with Ethernet Encapsulation)	95
Editing TCP/IP Options (with PPTP Encapsulation)	97
Editing TCP/IP Options (with PPPoE Encapsulation)	99
Remote Node Filter	99
IP Static Route Setup	101
IP Static Route Setup	102
Filter Configuration	107
About Filtering	107
The Filter Structure of the Prestige	108
Configuring a Filter Set	110
Filter Rules Summary Menu	112
Configuring a Filter Rule	113
TCP/IP Filter Rule	113
Generic Filter Rule	118
Example Filter	120
Filter Types and NAT	123
Applying a Filter and Factory Defaults	124
LAN traffic	124
Remote Node Filters	125
UPnP	127
Introducing Universal Plug and Play	127
How do I know if I'm using UPnP?	127
NAT Transversal	127
Cautions with UPnP	128
UPnP and ZyXEL	128
Configuring UPnP	128
Installing UPnP in Windows Example	130
Using UPnP in Windows XP Example	132
SNMP Configuration	137
About SNMP	137
Supported MIBs	139
SNMP Configuration	139
SNMP Traps	140
Traffic Redirect	143
Traffic Redirect	143
Traffic Redirect Setup	145
System Information & Diagnosis	149
System Status	149
To get to the System Status:	150
System Information and Console Port Speed	151
System Information	152
Console Port Speed	153
Log and Trace	154
Viewing Error Log	154
UNIX Syslog	155
Call-Triggering Packet	158
Diagnostic	159
WAN DHCP	160
Firmware and Configuration File Maintenance	163
Filename Conventions	163
Backup Configuration	164
Using the FTP Command from the DOS Prompt	165
Backup Configuration Using TFTP	167
TFTP Command Example	167
Backup Via Console Port	168
Restore Configuration	170
Restore Using FTP or TFTP	170
Restore Via Console Port	172
Uploading Firmware and Configuration Files	173
Firmware File Upload	174
Configuration File Upload	174
TFTP File Upload	176
Uploading Via Console Port	177
System Maintenance & Information	181
Command Interpreter Mode	181
Call Control Support	182
Budget Management	183
Call History	184
Time and Date Setting	185
Time Update Frequency	187
Remote Management	189
Telnet	189
FTP	189
Web	189
DNS (Domain Name System)	190
SNMP (Simple Network Management Protocol)	190
Remote Management Setup	190
Remote Management Limitations	192
Remote Management and NAT	192
System Timeout	192
Call Scheduling	193
Introduction	193
Schedule Setup	193
Schedule Set Setup	194
Applying Schedule Sets to Remote Nodes	196
Troubleshooting	199
Problems Starting Up the Prestige	199
Problems with the LAN Interface	199
Problems with the WAN Interface	200
Problems with Internet Access	201
Appendix APPPoE	203
Appendix B PPTP	206
Appendix DBoot Commands	209
Appendix ENetBIOS Filter Commands	211
Log Descriptions	214
Appendix FPower Adapter Specifications	218
Appendix FHardware Specifications	219

Match case Limit results 1 per page

Prestige 314 PLUS Broadband Sharing Gateway with 4-Port Switch

4-2

NAT

NAT never changes the IP address (either local or global) of an

outside

host.

4.1.2 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 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, e.g., 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 (for Many-to-One and Many-to-Many

Overload mapping – see

Table 4-2

), NAT offers the additional benefit of firewall protection. If no server is

defined in these cases, all incoming inquiries will be filtered out by your Prestige, thus preventing intruders

from probing your network. For more information on IP address translation, refer to

RFC 1631

The IP

Network Address Translator (NAT).

4.1.3 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 (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 Prestige keeps track of the original addresses and port numbers so incoming

reply packets can have their original values restored. The following figure illustrates this.