Cisco PIX 525 Especificações descarregar pdf (Página 187)

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101

CHAPTER

12-1

Cisco Security Appliance Command Line Configuration Guide

OL-6721-01

Firewall Mode Overview

This chapter describes how the firewall works in each firewall mode.

The security appliance can run in two firewall modes:

• Routed mode

• Transparent mode

In routed mode, the security appliance is considered to be a router hop in the network. It can perform

NAT between connected networks, and can use OSPF or passive RIP (in single context mode). Routed

mode supports many interfaces. Each interface is on a different subnet. You can share interfaces between

contexts.

In transparent mode, the security appliance acts like a “bump in the wire,” or a “stealth firewall,” and is

not a router hop. The security appliance connects the same network on its inside and outside interfaces.

No dynamic routing protocols or NAT are used. However, like routed mode, transparent mode also

requires access lists to allow any traffic through the security appliance, except for ARP packets, which

are allowed automatically. Transparent mode can allow certain types of traffic in an access list that are

blocked by routed mode, including unsupported routing protocols. Transparent mode can also optionally

use EtherType access lists to allow non-IP traffic. Transparent mode only supports two interfaces, an

inside interface and an outside interface, in addition to a dedicated management interface, if available

for your platform.

Note The transparent firewall requires a management IP address. The security appliance uses this IP address

as the source address for packets originating on the security appliance. The management IP address must

be on the same subnet as the connected network.

This chapter includes the following sections:

• Routed Mode Overview, page 12-1

• Transparent Mode Overview, page 12-8

Routed Mode Overview

• IP Routing Support, page 12-2

• Network Address Translation, page 12-2

• How Data Moves Through the Security Appliance in Routed Firewall Mode, page 12-3

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