Cisco PIX 525 Spécifications télécharger pdf (Page 190)

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Cisco Security Appliance Command Line Configuration Guide

OL-6721-01

Chapter 12 Firewall Mode Overview

Routed Mode Overview

An Inside User Visits a Web Server

Figure 12-2 shows an inside user accessing an outside web server.

Figure 12-2 Inside to Outside

The following steps describe how data moves through the security appliance (see Figure 12-2):

1. The user on the inside network requests a web page from www.example.com.

2. The security appliance receives the packet and because it is a new session, the security appliance

verifies that the packet is allowed according to the terms of the security policy (access lists, filters,

AAA).

For multiple context mode, the security appliance first classifies the packet according to either a

unique interface or a unique destination address associated with a context; the destination address

is associated by matching an address translation in a context. In this case, the interface would be

unique; the www.example.com IP address does not have a current address translation in a context.

3. The security appliance translates the local source address (10.1.2.27) to the global address

209.165.201.10, which is on the outside interface subnet.

The global address could be on any subnet, but routing is simplified when it is on the outside

interface subnet.

4. The security appliance then records that a session is established and forwards the packet from the

outside interface.

Web Server

10.1.1.3

www.example.com

User

10.1.2.27

209.165.201.2

10.1.1.110.1.2.1

Source Addr Translation

209.165.201.1010.1.2.27

Outside

Inside DMZ

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