Cisco PIX 525 Spécifications télécharger pdf (Page 165)

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Cisco PIX Firewall and VPN Configuration Guide

78-15033-01

Chapter 4 Using PIX Firewall in SOHO Networks

Using the PIX Firewall PPPoE Client

PPPoE provides a standard method of employing the authentication methods of the Point-to-Point

Protocol (PPP) over an Ethernet network. When used by ISPs, PPPoE allows authenticated assignment

of IP addresses. In this type of implementation, the PPPoE client and server are interconnected by Layer

2 bridging protocols running over a DSL or other broadband connection.

PPPoE is composed of two main phases:

• Active Discovery Phase—In this phase, the PPPoE client locates a PPPoE server, called an access

concentrator. During this phase, a Session ID is assigned and the PPPoE layer is established.

• PPP Session Phase—In this phase, PPP options are negotiated and authentication is performed.

Once the link setup is completed, PPPoE functions as a Layer 2 encapsulation method, allowing data

to be transferred over the PPP link within PPPoE headers.

At system initialization, the PPPoE client establishes a session with the access concentrator by

exchanging a series of packets. Once the session is established, a PPP link is set up, which includes

authentication using Password Authentication protocol (PAP). Once the PPP session is established, each

packet is encapsulated in the PPPoE and PPP headers.

Configuring the PPPoE Client Username and Password

To configure the username and password used to authenticate the PIX Firewall to the access

concentrator, use the PIX

Firewall vpdn command. The vpdn command is used to enable remote access

protocols, such as L2TP, PPTP, and PPPoE. To use the vpdn command, you first define a VPDN group

and then create individual users within the group.

To configure a PPPoE username and password, perform the following steps:

Step 1 Define the VPDN group to be used for PPPoE, by entering the following command:

vpdn group group_name request dialout pppoe

In this command, replace group_name with a descriptive name for the group, such as “pppoe-sbc.”

Step 2 If your ISP requires authentication, select an authentication protocol by entering the following

command:

vpdn group group_name ppp authentication PAP|CHAP|MSCHAP

Replace group_name with the same group name you defined in the previous step. Enter the appropriate

keyword for the type of authentication used by your ISP:

• PAP—Password Authentication Protocol

• CHAP—Challenge Handshake Authentication Protocol

• MS-CHAP—Microsoft Challenge Handshake Authentication Protocol

Note When using CHAP or MS-CHAP, the username may be referred to as the remote system name,

while the password may be referred to as the CHAP secret.

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Cisco PIX 525 Spécifications Page 165