Cisco PIX 525 Spezifikationen PDF herunterladen (Seite 28)

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Cisco PIX Firewall and VPN Configuration Guide

78-15033-01

Chapter 1 Getting Started

Controlling Network Access

• Access Control, page 1-6

• VLAN Support, page 1-8

Chapter 2, “Establishing Connectivity” provides configuration instructions for establishing network

connectivity through the PIX Firewall. Chapter 3, “Controlling Network Access and Use” provides

configuration instructions for using the PIX Firewall to control network connectivity.

How the PIX Firewall Works

The PIX Firewall protects an inside network from unauthorized access by users on an outside network,

such as the public Internet. Most PIX

Firewall models can optionally protect one or more perimeter

networks, also known as demilitarized zones (DMZs). Access to the perimeter network is typically less

restricted than access to the inside network, but more restricted than access to the outside network.

Connections between the inside, outside, and perimeter networks are controlled by the PIX

Firewall.

To effectively use a firewall in your organization, you need a security policy to ensure that all traffic from

the protected networks passes only through the firewall to the unprotected network. You can then control

who may access the networks with which services, and how to implement your security policy using the

features that the PIX

Firewall provides.

Figure 1-1 shows how a PIX Firewall protects a network while allowing outbound connections and

secure access to the Internet.

Figure 1-1 The PIX Firewall in a Network

Protected servers

No direct

inbound

connections

Inside Outside

Router

Internet

attached router

PIX

Firewall

Outbound

connections

Protected clients

Server 1

Server 2

Internet

accesible server

S6243

Perimeter

Within this architecture, the PIX Firewall forms the boundary between the protected networks and the

unprotected networks. All traffic between the protected and unprotected networks flows through the

firewall to maintain security. Traffic may not exit the PIX Firewall on the same network interface it

entered. The unprotected network is typically accessible to the Internet. The PIX

Firewall lets you locate

servers such as those for Web access, SNMP, electronic mail (SMTP) in the protected network, and

control who on the outside can access these servers.

For PIX Firewall models with three or more interfaces, server systems can be located on a perimeter

network as shown in

Figure 1-1, and access to the server systems can be controlled and monitored by the

PIX Firewall. The PIX 501 and PIX 506/506E each have two network interfaces, so all systems must be

located either on the inside or the outside interfaces.

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