Microsoft 2004 Manuel D’Utilisation

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ISA Server 2004 Configuration Guide 23 
Introduction 
The Microsoft Internet Authentication Server (IAS) is an industry standard RADIUS server that 
can be used to authenticate users connecting to the ISA Server 2004 firewall machine. You 
can use IAS to authenticate Web Proxy clients on the internal network and VPN clients and 
VPN gateways calling in from an external network location. In addition, you can use RADIUS 
authentication to remote users who connect to Web servers published using ISA Server 2004 
Web Publishing rules. 
The major advantage of using RADIUS authentication for Web proxy and VPN connections is 
that the ISA Server 2004 firewall computer does not need to be a member of the domain to 
authenticate users whose accounts are contained in the Active Directory on the internal 
network. Many firewall administrators recommend that the firewall not be a member of the 
user domain. This prevents attackers who may compromise the firewall from taking 
advantage of the firewall’s domain member status to amplify an attack against the internal 
network. 
One major drawback to not making the ISA Server 2004 firewall a member of the internal 
network domain is that you cannot use the Firewall client to provide authenticated access to 
all TCP and UDP protocols. For this reason, we make the ISA Server 2004 firewall computer 
a member of the domain in this ISA Server 2004 Configuration Guide series. However, if 
you choose to not join the firewall to the domain, you can still use IAS to authenticate your 
VPN and Web Proxy clients. 
We will discuss the following procedures in this document: 
•  Installing the Microsoft Internet Authentication Service 
•  Configuring the Microsoft Internet Authentication Service