NAT Configuration Task List 1815streaming protocol (RTSP), H.323, Netmeeting 3.01, and NetBIOS over TCP/IP(NBT).n The support for the special protocols varies by device models.NAT multiple-instanceThis feature allows users from different MPLS VPNs to access external networksthrough the same outbound interface. It also allows them to have the sameinternal network address. The process works as follows:When an MPLS VPN user communicates with an external network, NAT replacesits internal IP address and port number with the NAT gateway’s external IP addressand port number. It also records the relevant MPLS VPN information, such as theprotocol type and router distinguisher (RD for short). When the response packetarrives, the NAT gateway then restores the external IP address and port number tothe internal IP address and port number. Additionally, the NAT gateway canidentify the users who access the external network. Besides NAT, NAPT alsosupports multiple-instance.The multiple-instance feature can also apply to internal servers so that externalusers can access an internal host of an MPLS VPN. For example, in MPLS VPN1, thehost that provides WWW service has an internal address 10.110.1.1. The host canuse 202.110.10.20 as an external IP address so that the Internet users can accessthe WWW service in MPLS VPN1 through this external address.NAT ConfigurationTask ListFollow the following steps to configure NAT:To do... Use the command... RemarksEnter system view system-view -Define an addresspoolnat address-groupgroup-number start-addressend-addressOptionalNot necessary when the router has beenconfigured with Easy IP.Configure addresstranslationRefer to “ConfiguringAddress Translation” onpage 1816RequiredConfigure an internalserverRefer to “ConfiguringInternal Server” on page1818OptionalConfigure NAT agingtimenat aging-time { default |{ dns | ftp-ctrl | ftp-data |icmp | pptp | tcp | tcp-fin |tcp-syn | udp } seconds }OptionalBy default, NAT aging time varies byprotocols:60 seconds for DNS;7,200 seconds for FTP ctrl;300 seconds for FTP data;60 seconds for ICMP;86,400 seconds for PPTP;86,400 seconds for TCP;60 seconds for TCP fin, TCP rst,3600 seconds for TCP syn;300 seconds for UDP.
