NAT/PAT - Konfiguration in CISCO

NAT = Network Address Translation

PAT = Port Address Translation
PAT -> Die lokalen Netze bekommen die gleiche IP-Adresse im öffentlichen Netz (die vom Router)

Allgemeines:

NAT ist ein Verfahren, welches in IP-Routern eingesetzt wird, um lokale Netzwerke mit dem Internet zu verbinden.
Private Addressen besitzen in öffentlichen Netzen keine Gültigkeit. Stationen mit einer privaten IP-Adresse können daher nicht mit Stationen außerhalb des lokalen Netzwerks kommunizieren.

Damit aber trotzdem alle Computer mit privaten IP-Adressen Zugang zum Internet bekommen können, muss ein Internet-Zugangs-Router in allen ausgehenden Datenpaketen die IP-Adressen der lokalen Stationen, durch die eigene, öffentliche IP-Adresse ersetzen.

Der NAT-Router merkt sich anhand einer Tabelle, welche Datenpakete zu welche TCP-Verbindung gehören.

Weitere Informationen können hier gefunden werden:
http://www.elektronik-kompendium.de

NAT in CISCO:

For this, let's watch this video:

https://www.youtube.com/watch?v=FfPJ_dvM_is

Summary of steps to configure PAT:

• Identify the inside and outside interfaces
• Create an access-control list to identify and permit the traffic flow
• Apply the ACL (Access Control List) to the outside interface and enable NAT overloading

Here are a few nice examples:

CISCO Example NAT/PAT

Basic Example NAT & PAT

Projekt: Verschiedene Städte

 Aufgabenstellung:

NAT/PAT, Routing Protocols

In this lab you should plan the following computer network for a medium sized company. There are about 250 employees on three sites (Klagenfurt, Villach and Feldkirchen). Every employee has a laptop/PC and at least one smartphone and/or tablet computer. In sum there are 12 departments and each department runs its own server. The sites are connected via leased lines and at the main site (Klagenfurt) there are also the public servers for E-Mail, Web etc. and the access to the public internet. The company has the public internet adddresses 178.32.43.192/26 and 2a30:2345:1::/48.

Please do the following tasks:

1. Plan the network topology for redundant access to the main site. Also the departments should have a redundant access to the main switch.
2. For security reasons please do subnetting as much as possible. 
3. For IPv4 you should you use private internet addresses and do NAT/PAT.
4. For WLAN access you should consider to use access points.
5. Draw the topology with Cisco Packet Tracer. For simplicity you don't have to draw each PC/laptop/smartphone. It's sufficient to simulate two PCs in each subnet. 
6. For routing you should use suitable routing protocols. (OSPF!)
7. For testing please consider some scenarios, e.g. links get broken, devices fail, etc.