Bài giảng Mạng máy tính nâng cao - Chapter 12: Network adress translation

Chapter 12NETWORK ADRESS TRANSLATION MẠNG MÁY TÍNH NÂNG CAOObjective Identify private IP addresses as described in RFC 1918 Discuss characteristics of NAT and PAT Explain the benefits of NAT Explain how to configure NAT and PAT, including static translation, dynamic translation, and overloading Identify the commands used to verify NAT and PAT configuration List the steps used to troubleshoot NAT and PAT configuration Private addresses NAT provides great benefits to individual companies and the Internet. Before NAT, a host with a private address could not access the Internet. Using NAT, individual companies can address some or all of their hosts with private addresses and use NAT to provide access the Internet. Introducing NAT and PATNAT enable networks to use private IP addresses on internal networks. These private, internal addresses are translated to routable, public addresses. A NAT enabled device typically operates at the border of a stub network. A stub network is a network that has a single connection to its neighbor network Introducing NAT and PAT This section uses the following terms when discussing NAT:Inside local address - Usually not an IP address assigned by RIR (Regional Internet Registry) or service provider and is most likely an RFC 1918 private address. In the figure, the IP address 192.168.10.10 is assigned to the host PC1 on the inside network. Inside global address - Valid public address that the inside host is given when it exits the NAT router. When traffic from PC1 is destined for the web server at 209.165.201.1, router R2 must translate the address. In this case, IP address 209.165.200.226 is used as the inside global address for PC1.Introducing NAT and PATOutside global address - Valid public IP address assigned to a host on the Internet. For example, the web server is reachable at IP address 209.165.201.1. Outside local address - The local IP address assigned to a host on the outside network. In most situations, this address will be identical to the outside global address of that outside device. Note: In this course, we will be referencing the inside local address, inside global address, and the outside global address. The use of the outside local address is outside the scope of this course. Major NAT and PAT features Static NAT is designed to allow one-to-one mapping of local and global addresses. Dynamic NAT is designed to map a private IP address to a public address. Any IP address from a pool of public IP addresses is assigned to a network host. Overloading, or Port Address Translation (PAT), maps multiple private IP addresses to a single public IP address. Multiple addresses can be mapped to a single address because each private address is tracked by a port number. PAT uses unique source port numbers on the inside global IP address to distinguish between translations. Major NAT and PAT featuresSee more NATMajor NAT and PAT featuresConfiguring Static NAT Configuring Static NATConfiguring Static NAT Configuring Dynamic NAT Configuring Dynamic NATConfiguring PAT Configuring PATConfiguring PAT Verifying NAT and PAT configuration Verifying NAT and PAT configuration Troubleshooting NAT and PAT configuration