Router NAT Setup Detailed

With the rapid development of Internet network, the shortage of IP address has become a very prominent problem. In order to solve this problem, there are many solutions. The following are some of the more effective ways to address translation (NAT) in the current network environment.

Nat settings can be divided into static address translation, dynamic address translation, and multiplex dynamic address conversion.

1. Static address Translation applicable environment

Static address translation Converts an internal local address to an internal legal address, and it needs to specify and which legal address to convert. If the internal network has services such as an e-mail server or an FTP server that can be provided to external users, the IP addresses of these servers must be converted to static addresses so that they can be used by external users.

Static address translation Basic configuration steps:

(1) Establishing static address conversion between internal local address and internal legal address. Enter in global setting state:

Ip nat inside source static internal local address internal legal address

(2), specify the internal port of the connection network to enter in the Port settings state:

IP nat Inside

(3) Specifies that the external port connecting the external network is entered in the Port setting state:

IP Nat Outside

Note: You can define multiple internal ports and multiple external ports according to your actual needs.
This example realizes the static NAT address translation function. Use 2501 of the Ethernet port as the internal and sync port 0 as the external port. Where 10.1.1.2,10.1.1.3,10.1.1.4 's internal local address is static address translation. Its internal legal address corresponds to 192.1.1.2,192.1.1.3,192.1.1.4 respectively.

Configuration of Router 2501:

Current configuration:

Version 11.3

No service password-encryption

Hostname 2501

IP nat inside source static 10.1.1.2 192.1.1.2

IP nat inside source static 10.1.1.3 192.1.1.3

IP nat inside source static 10.1.1.4 192.1.1.4

Interface Ethernet0

IP address 10.1.1.1 255.255.255.0

IP nat Inside

Interface Serial0

IP address 192.1.1.1 255.255.255.0

IP Nat Outside

No IP mroute-cache

Bandwidth 2000

No Fair-queue

Clockrate 2000000

Interface Serial1

No IP address

Shutdown

No IP classless

IP Route 0.0.0.0 0.0.0.0 Serial0

Line con 0

Line aux 0

Line vty 0 4

Password Cisco

End

After the configuration is complete, you can view it with the following statement:

Show ip Nat Statistcs

Show ip NAT Translations

2, dynamic address conversion applicable to the environment:

Dynamic address translation is also a one-to-one conversion of the local address to the internal legal address, but the dynamic address translation converts the internal local address dynamically from the internal legal address pool by selecting a last-used address.

Dynamic address Translation Basic configuration steps:

(1), in the global setting mode, define the internal legal address pool

IP NAT Pool Address pool name Start IP address IP address subnet mask

Where the address pool name can be set arbitrarily.

(2), in global settings mode, define a standard access-list rule to allow which internal addresses can be dynamic address conversion.

Access-list Label permit Source address wildcard character

An integer with a label of 1-99.

(3), in Global settings mode, address translation is made to the internal local address specified by Access-list and the specified internal legal address pool.

IP NAT inside source list access list label pool internal legal address pools name

(4), specify the internal port connected to the internal network in the Port settings state:

IP nat Inside

(5), specifying external ports connected to the external network

Ip Nat Outside