3Com Router 3000 Ethernet FamilyConfiguration Guide Chapter 11 NAT Configuration3Com Corporation11-7rules. For the involved protocol, this is transparent. So far, V 2.41’s NAT ALGimplementation supports point to point tunneling protocol (PPTP), DNS, FTP, Internetlocator service (ILS), NetBIOS over TCP/IP (NBT), session initiation protocol (SIP), andH.323.11.2.8 Multi-Instance of MPLS VPN NAT SupportedNAT multi-instance function offers a solution that allow not only the VPN users toaccess the Internet from inner network, but also the MPLS VPN users to access theInternet through a single gateway, as well as the users from different VPNs to use thesame private address. When an MPLS VPN user wants to access the Internet, NATtranslates the IP address and the port of the internal host into external IP address andport and records the MPLS VPN information (such as protocol type and route identifierRD) about the user. When the packet is sent back, NAT restores the external IPaddress and port to the IP address and port of the internal host, and recognizes theMPLS VPN user. No matter what kind of NAT it is, PAT or NO-PAT, multi-instance will besupported.V 2.41 NAT supports the multi-instance of internal server, and provides the outsidenetwork with the access to the hosts within MPLS VPN. For example, the WWW serverin VPN1 uses the address of 10.110.1.1 as the inner address, on the other hand, usesthe address of 202.110.10.20 as the outer address. Using the outer address(202.110.10.20), the Internet users can get the WWW service provided by MPLSVPN1.11.3 NAT ConfigurationNAT configuration includes:z Configure address poolz Configure NATz Configure Easy IPz Configure static NATz Configure many-to-many NATz Configure NAPTz Configure internal serverz Configure NAT ALGz Configuring NAT entries for domain namesz Configure NAT effective time (optional)11.3.1 Configuring Address PoolThe address pool is a collection of some consecutive IP addresses, while internal datapacket needs to access external network via NAT, a certain address in the address pool
