3Com Router 3000 Ethernet FamilyConfiguration Guide Chapter 11 NAT Configuration3Com Corporation11-1611.5.2 Configuration Example of NAT Using IP Address of LoopbackInterfaceI. Network requirementsAs shown in Figure 11-5, the intranet accesses the Internet through the serial interface3/0/0 on the 3Com router; the internal network segment 10.110.10.0/24 can access theInternet, but other network segments cannot; the internet network segment uses theLoopback interface address 202.38.160.106 as the converted address. The intranetprovides WWW, FTP and SMTP services to the outside, and the three servers use thesame public address 202.38.160.100.II. Network diagramInternal PC10.110.10.100 10.110.12.100DDN10.110.10.1 10.110.10.2 10.110.10.3 10.110.10.4FTP server SMTP serverWWWserver 2WWWserver 1RouterIntranetInternal PCOutside PCFigure 11-5 Configuration network diagramIII. Configuration procedure# Configure an ACL.[3Com] acl number 2001[3Com-acl-basic-2001] rule permit source 10.110.10.0 0.0.0.255[3Com-acl-basic-2001] rule deny source 10.110.0.0 0.0.255.255[3Com-acl-basic-2001] quit# Configure the loopback interface.[3Com] interface loopback0[3Com-LoopBack0] ip address 202.38.160.106
