Netcom NB9W manual Advanced NAT Explanation

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Advanced > NAT > Explanation

NAT stands for Network Address Translation, a process which converts private IP addresses of a computer on the internal private network to one or more public IP addresses for the Internet. NAT changes the packet headers to the new address and keeps track of each session; when packets come back from the Internet, it performs the reverse conversion to the IP address of the client machine.

Web applications operate through ‘open ports’ on devices attached to the Internet by initiating a query which opens a ‘communication session’ with the host through the open port. The presence of the NAT device prevents this process from occurring, as the NAT only admits incoming packets that have been elicited by an outgoing request; other packets are discarded.

However this causes connectivity problems, as any requests originating from applications on the other side of the NAT device - such as requests generated by network gaming and conferencing applications - will not be able to locate a port, and therefore a host, with which to communicate, as their requests are discarded by the NAT. Hence the terms ‘opening’, ‘forwarding’ and ‘mapping’ ports: these processes add information to the NAT table which allows the NAT router to direct incoming requests from selected applications to the appropriate port.

So Port Mapping tells the NAT router: ‘when a request arrives which is intended for TCP port 1357, don’t discard it, but direct it to such-and-such a port’. The port-mapping process invokes advanced routing functionality to ‘bind’ the Port Mapping request to the LAN client from which it originated.

A basic NAT operation is depicted in this illustration:

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NB9/NB9W ADSL2+ VoIP Router

 

YML790 Rev8

Image 48
Contents User Guide Your ADSL2+ connection Contents Save & Reboot Wireless NB9W only OverviewAdsl Broadband VoIP Voice over Internet ProtocolNB9/NB9W Package Contents Selected terminology used in this manualDo I need a micro filter? Multi-purpose Gateways and In-line SplittersMinimum System Requirements PC RequirementsAdsl Requirement VoIP RequirementsColour Mode Function Getting to Know the NB9/NB9WNB9W only Ethernet Hub / Switch Your Adsl and telephone serviceSettings Back Panel PortsDefault Settings Restore Factory Default SettingModem Access LAN ManagementConnecting the NB9/NB9W RJ-11 Telephone line RJ-45 Ethernet cableConnecting the Cables Establishing an Adsl connection via PPPoE NB9/NB9W ADSL2+ VoIP Router Establishing your Wireless Connection for NB9W only Security WEP 64-bit HEX keySetting up your VoIP account Interface Name Don’t change the ‘Interface name’ setting Computer Hardware Configuration Windows XP PCsWindows 2000 PCs Windows Me PCsWindows 95, 98 PCs Mac OSXWindows Vista Digging Deeper Advanced Settings Version of the bootloader BasicBasicHome Field DescriptionBasicADSL Quick Setup Completed you will be returned to the ‘Basic Home’Voice Settings VoiceAbout SIP & VoIP About SIPVoice Menu Field ValueField Means VoIP Status Indicator Means Voice Dial Plan Voice Dial Plan OutgoingVoice Dial Plan Incoming Voice Dial Plan Advance Wireless NB9W only Wireless SetupField Enter SsidWireless Security Quick Setup Quick Security Setup 1 WEP SecurityQuick Security Setup 2 WPA-PSK Wireless Security in Detail Authentication and EncryptionNetwork Keys Network Authentication WEP and WPA802.1X SharedTkip AESDependent on vendor driver support TKIP+AESWPA2 Wireless Configuration Field Name AboutSmaller packet without using RTS/CTS Messages. The default isBuffered frames at the access point WMM Wi-Fi MultimediaWireless Mac Filter How to find your MAC addressField Name Comment Wireless Bridge Wireless Station InfoAvailable bridges Management Device Settings Backup Management Device Settings UpdateManagement Device Settings Restore Default ManagementManagement Device Settings Update Firmware Management SnmpAccess Control Services Management SntpAccess Control IP Addresses Access Control PasswordSave & Reboot Advanced Advanced WANField Choosing a WAN Profile Alternative Connection Types Inc PPPoA Advanced LAN Enable Igmp Snooping Table entryThrough your NB9/NB9W Advanced NAT Explanation Advanced NAT Port Forwarding External Port Start External Port EndLast port in the range here Would select UDPAdvanced NAT Port Triggering Application Outgoing Port Reply PortICQ ICUAdvanced NAT DMZ Advanced Security IP Filtering Advanced Security Parental Control Advanced QoS UDPNB9/NB9W ADSL2+ VoIP Router Advanced Routing Default Gateway Advanced Routing Static Route Field EntryRemote router gateway address Advanced Routing Dynamic Route Advanced DNS DNS ServerAdvanced DNS Dynamic DNS Advanced DSLStatus Diagnostics StatusStatus System Log Status Statistics Status WANStatus Route Status ARPStatus Dhcp Status BridgingStatus Igmp Proxy Appendix a Troubleshooting Problems with LANProblems with WAN Problem with Wireless Windows XP service pack NB9/NB9W ADSL2+ VoIP Router YML790 Rev8 Mac OSX Windows Vista NB9/NB9W ADSL2+ VoIP Router NB9/NB9W ADSL2+ VoIP Router YML790 Rev8 NB9/NB9W ADSL2+ VoIP Router Now the connection is ready Appendix C How to change Wireless Security on your NB9W WEP encryptionWPA encryption Appendix D Glossary DSL FTPGGP GRENIC RIPSdns SnmpTCP TCP/IPTftp TTLAppendix F Registration and Warranty Information Contact InformationCopyright Information Customer InformationProduct Warranty Limitations of WarrantyGNU General Public License NB9/NB9W ADSL2+ VoIP Router Purchase by Phone Click on the Buy Now buttonProduct Warranty Contact Information