Cisco router NAT configuration overview

With the development of the routing industry, the market demand is more extensive, but many users still do not understand the routing configuration issues. Here we mainly provide a comprehensive description of the Cisco router NAT configuration. More and more INTERNET resource sharing methods are available. In most cases, ddnleased lines are widely used with their stable performance and good scalability.

DDN connection is simple in terms of hardware requirements. Only one router (router) and proxy server are required, however, system configuration is a tough issue for many network administrators. The following uses a CISCO router as an example to describe several successful Cisco router NAT configuration methods for reference:

1. Configure to access INTERNET resources directly through a vro 

Under normal circumstances, when a workstation inside the Organization directly uses a route for external access, it will be filtered out by the router because the workstation uses a reserved address on the Internet, as a result, Internet resources cannot be accessed. The solution to this problem is to use the NATNetwork Address Translation function provided by the routing operating system to convert private addresses on the Intranet to valid addresses on the Internet, this allows users with invalid IP addresses to access the Internet through NAT. In this way, you do not need to configure a proxy server to reduce investment, save valid IP addresses, and improve the security of the internal network.

NAT has two types: Single mode and global mode. The NAT single mode maps many local LAN hosts into an Internet address just like its name. All hosts in the LAN are regarded as Internet users for External Internet networks. The host in the local LAN continues to use the local address.

In the global mode of NAT, the router interface maps many local LAN hosts into an IP address pool with a certain Internet address range ). When the local host port is connected to a host on the Internet, an IP address in the IP address pool is automatically assigned to the local host. After the connection is interrupted, the dynamically assigned IP address is released, the released IP address can be used by other local hosts.

The following uses the network environment of our Organization as an example to list the NAT configuration methods and processes of Cisco routers for your reference.
Our company uses China Unicom Optical Cable V.35) to access the INTERNET. The router is CISCO2610 and the LAN uses the INTEL550 M switch. China Unicom provides us with the following four IP addresses:

211.90.137.25255.255.255.252) Wan port used for the local Router
211.90.137.2620.0000252) port used for peer connection
211.90.139.41255.20.252) at your disposal
211.90.139.42255.255.255.252) for your own control

2. About Cisco router NAT configuration

Note: All workstations in the school are connected to switches. Routers are also connected to internal switches through Ethernet ports. The Ethernet ports on the routers use internal private addresses, the two valid IP addresses allocated by China Unicom are used at both ends of the optical fiber. In this connection mode, you only need to set NAT inside the vro to allow all workstations within the organization to access INTERNTE, on each workstation, you only need to set the gateway to point to the Ethernet port 192.168.0.3 of the router, and saves two valid IP addresses available for your own freedom, such as setting up your own WEB and E-MAIL server ). But there are also disadvantages: you cannot enjoy the CACHE service provided by the proxy server to speed up access. Therefore, the Cisco router NAT solution is suitable for a small number of workstation units. You can use the two methods described later when the number of workstation units is large. The vro configuration is as follows:

3. workstation configuration

Static IP addresses are required. You must set the IP address in the TCP/IP attribute and the Ethernet IP address of the 192.168.0.3 router, no special settings are required in Web browsers and other online tools.