Computer Networking and Management

Windows Server provides network address translation functionality as a part of the Routing and Remote Access service. NAT enables computers on small to medium-sized organizations or offices with private networks to admission resources on the Internet or other public network. Here in this technique computers on a private network are configured with private IPv4 addresses. The computers on a public network are enabled by globally unique IPv4.

A typical deployment is a small office or home office (SOHO), or a medium-sized business that uses Routing and NAT technology to enable computers on the internal corporate network to connect to resources on the Internet without having to deploy a proxy server.

When a client on the private network sends a request for information to a computer on the public network, the NAT-enabled router, located at the boundary between the private and the public networks, translates the outgoing packets and then sends them to the destination computer on the public network.

The router also translates the response from the public network resource and returns the response to the client on the local network.

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Figure 1 Shows the NAT components and their relation to TCP/IP and other router components. [grc. org] NAT (network address translation) Facilities The Windows Server 2003 Routing and Remote Access implementation of NAT gives you the following solutions to problems faced by small networks: Reusing IP addresses Bundling NAT, DHCP, and DNS functionality for small networks Providing Internet access to remote access clients

Providing PPPoE broadband Internet access Operation of NAT Router Here I describe to make a network connection firest I describe a few things about NAT router.

NAT router should be configured to use blocks of non-public, private IP addresses. It is on Routers to decide whether it will route local data packets upstream, out of their WAN port based upon whether or not the packet's destination IP address falls within the local LAN address range. So that, the IP address that is assigned to a router's WAN port must lie outside the address range the router is using for its LAN-side addresses.

These two simple rules, a typical two-router configuration could be setup with the external NAT router configured to give the LAN addresses in the 192. 168. 1. Range and the internal router configured to issue its LAN addresses from the non-overlapping range 192. 168. 2. So that the internal router's DHCP client would receive an address for its WAN port from the external router's LAN range like pervious address (192. 168. 1. ), no address it receives. Where the third address byte is "1" . Could possibly have contradiction with any of the 192. 168. 2.

Addresses it will be assigning to its own machines. So that the internal router will always be able to determine whether data packets are attached for other machines within its LAN, or need to be "routed" out of its WAN port. If your routers give the 3rd number of their LAN networks to be user specified and configured, while conveying the final address byte automatically as needed, you can sequentially and uniquely number every NAT router within your network, and use that number as the third address byte assigned to machines within that router's LAN network.

In this way, EVERY computer will have a unique private address. None of the private LAN networks will be overlapping. And so that there will never be any collision with the Internet's public IP space (Tenenbom, 1996) . Figure 2 NAT router With an Eathernet connection. (GRC. com) Making the electrical connection Now going to describe the basic operation involve in making a Ethernet connection with a NAT enabled router.

Standard Ethernet network cables with standard RJ-45 Male connectors are wired straight through. This means that pin one at one end is wired to pin 1 at the other end, pin 2 connects to pin 2, and like this sequence all 8 pins are arranged. Here this means that pins that are connecting to signal outputs at one end of the cable need to connect to signal inputs at the other. This is handled mechanically for users by having their RJ-45 Female counterparts available in two different signal arrangements.

PC Ethernet adapters uniformly use 1 set of pins for inputs and outputs, and Ethernet switches and hubs intentionally use the reverse arrangement. This allows PC adapters A to be plugged directly into switches and hubs B with straight through cable. So that a NAT router's LAN ports are meant to be plugged directly into PCs A, the router's LAN-side connections have the arrangement of switches and hubs B. But since a NAT router's WAN port is meant to emulate and take the place of a single PC. Router's WAN-side connection is that of a PC A.

This expediently means that the WAN connection from internal NAT routers, which appear to be PC's. So that these connections can be plugged directly into the LAN ports of another NAT router using a standard straight through Ethernet cable. So that as long as you have configured each NAT router on your network to have different and non-overlapping WAN side and LAN side networks, all of the DHCP clients and servers should interact correctly, and packets should all be routed exactly the way you want (Tenenbom, 1996).