Cisco PIX 525 Spezifikationen PDF herunterladen (Seite 199)

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101

12-13

Cisco Security Appliance Command Line Configuration Guide

OL-6721-01

Chapter 12 Firewall Mode Overview

Transparent Mode Overview

An Inside User Visits a Web Server

Figure 12-9 shows an inside user accessing an outside web server.

Figure 12-9 Inside to Outside

The following steps describe how data moves through the security appliance (see Figure 12-9):

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

2. The security appliance receives the packet and adds the source MAC address to the MAC address

table, if required. Because it is a new session, it 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 a unique

interface.

3. The security appliance and records that a session is established.

4. If the destination MAC address is in its table, the security appliance forwards the packet out of the

outside interface. The destination MAC address is that of the upstream router, 209.186.201.2.

If the destination MAC address is not in the security appliance table, the security appliance attempts

to discover the MAC address by sending an ARP request and a ping. The first packet is dropped.

5. When the web server responds to the request, the security appliance adds the web server

MAC address to the MAC address table, if required, and because the session is already established,

the packet bypasses the many lookups associated with a new connection.

6. The security appliance forwards the packet to the inside user.

Management IP

209.165.201.6

www.example.com

209.165.201.2

Host

209.165.201.3

Internet

92408

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