Shulou(Shulou.com)06/01 Report--

NAT network address translation

General situation of theory:

The concept of NAT: it automatically modifies the source IP address or destination IP address in the IP header. The verification of the IP address is done automatically during the NAT processing. It translates the private network IP address of the internal network into the only public network IP address in the world, so that the internal network can be connected to the Internet.

How to implement NAT:

1. Static translation (static translation): translates the private IP address of the internal network into a public legal IP address. The correspondence of IP addresses is one-to-one.

two。 Dynamic translation (dynamic translation): when an internal network is converted to a public network, the correspondence of IP addresses is uncertain and random.

3. Port address translation (port address translation,PAT): it changes the source IP address and source port of an outgoing packet and performs port translation. In other words, all hosts enjoy a legal IP address to achieve Internet access, maximize the saving of public network IP resources.

Here we simulate the choice of port address translation in order to solve the problem of IP address shortage, so here we will demonstrate by configuring a port address translation:

1. First of all, according to the experimental requirements, build the corresponding network topology diagram on the GNS3. As shown in the following figure:

two。 Next, we will VPC you to set the IP address for three PCs. As shown in the following figure:

3. Next, set up the switch sw. As shown in the following figure:

4. Next we will configure router R1. As shown in the following figure:

5. When everything is ready, the next step is PAT port address translation. Note: overload indicates the use of address reuse for PAT. As shown in the following figure:

6. Use PC1 and PC2ping to communicate with PC3, and we can turn on debug ip nat to see how the conversion is done. As shown in the following figure:

The experiment here is successful!

Summary:

The functions of NAT are:

1. Saving IP addresses, internal networks can use private IP to communicate with external networks

two。 The flexibility of communication between internal network and external network is enhanced.

3. Hiding the details of the internal network to avoid xxx from outside the network can play a certain security role.

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