Nat y vlan

ContentsIntroduction
Prerequisites
      Requirements
      Components Used
      Conventions
Quick Start Steps for Configuring and Deploying NAT
Defining NAT Inside and Outside Interfaces
Example: Allowing Internal Users to Access the Internet
      Configuring NAT to Allow Internal Users to Access the Internet
      Configuring NAT to Allow Internal Users to Access theInternet Using Overloading
Example: Allowing the Internet to Access Internal Devices
      Configuring NAT to Allow the Internet to Access Internal Devices
Example: Redirecting TCP Traffic to Another TCP Port or Address
      Configuring NAT to Redirect TCP Traffic to Another TCP Port or Address
Example: Using NAT During a Network Transition
      Configuring NAT for Use During a NetworkTransition
Example: Using NAT in Overlapping Networks
Difference between One-to-One Mapping and Many-to-Many
Verifying NAT Operation
Conclusion
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Introduction
This document explains configuring Network Address Translation (NAT) on a Cisco router for use in common network scenarios. The target audience of this documentis first time NAT users.
Note: In this document, when the internet, or an internet device is referred to, it means a device on any external network.
Prerequisites
Requirements
This document requires a basic knowledge of the terms used in connection with NAT. Some of the definitions can be found in NAT: Local and Global Definitions.
Components Used
The information in this document isbased on these software and hardware versions:
* Cisco 2500 Series Routers
* Cisco IOS® Software Release 12.2 (10b)
The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.Conventions
Refer to Cisco Technical Tips Conventions for more information on document conventions.
Quick Start Steps for Configuring and Deploying NAT
When you configure NAT, it is sometimes difficult to know where to begin, especially if you are new to NAT. These steps guide you to define what you want NAT to do and how to configure it:
1. Define NAT inside and outside interfaces.* Do users exist off multiple interfaces?
* Are there multiple interfaces going to the internet?
2. Define what you're trying to accomplish with NAT.
* Are you trying to allow internal users to access the internet?
* Are you trying to allow the internet to access internal devices (such as a mail server or web server)?
* Are you trying to redirect TCPtraffic to another TCP port or address?
* Are you using NAT during a network transition (for example, you changed a server's IP address and until you can update all the clients you want the non-updated clients to be able to access the server using the original IP address as well as allow the updated clients to access the server using the new address)?
* Are you using NAT to allowoverlapping networks to communicate?
3. Configure NAT in order to accomplish what you defined above. Based on what you defined in step 2, you need determine which of the following features to use:
* Static NAT
* Dynamic NAT
* Overloading
* Any combination of the above
4. Verify the NAT operation.
Each of these NAT examples guides you through steps 1 through 3 ofthe Quick Start Steps above. These examples describe some common scenarios in which Cisco recommends you deploy NAT.
Defining NAT Inside and Outside Interfaces
The first step to deploy NAT is to define NAT inside and outside interfaces. You may find it easiest to define your internal network as inside, and the external network as outside. However, the terms internal and external are subject to...