How to do NAT in 1603 router

Posted on 2003-03-06
Medium Priority
Last Modified: 2010-05-18
I am new to cisco. i am trying to configure 1603 router. I did it . i can access the internet.but the ISP is giving 2 fixed IP i wants to do natinfg in the router. Could u pls explain how to NAT in router. my internal network is  and the ISP given IP is astarting in 213.x.x.x .
Waiting for your valuable reply
Question by:jayan_k

Accepted Solution

pratigan earned 200 total points
ID: 8080352
Hello Jayan,

If your router uses NAT, it should be replacing the source IP of your private machines (192.x.x.x) with the public IP of the router (dynamically assigned by ISP) then sending it out.
The router fights invasion in a couple of different ways:

1) Prevents unknown computers from accessing the network ports on your PC, by hiding your actual PC's IP address. This is called Network Address Translation (NAT), and is a simple but effective block for preventing outside-in penetration. Basically, all a cracker could see would be your router's IP address, which doesn't have any programmability that he can attack.

2) An IP address filter, that sets up a hard block against certain IP addresses you specify in the router. This would be useful say, if you were China and wanted to block all communications with Google. It can also be used to prevent your teenagers from getting to Playboy.com, but most of these routers are a pain to configure for blocking, and some have a limit on the number of IP addresses they can filter.

Depending upon what you want to do, I would probably suggest that the NAT features are an effective way to prevent intrusion, and that if you needed to provide outbound security for web sites that you use something like NetNanny or other filtering program. These ARE updated frequently by their authors to contain all the new sites, and are a whole lot easier than trying to use the router admin program to add 50 sites a day...
Here are a few informational sites that may also be helpful.

Good Luck !!

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