Troubleshooting PPP

The configuration of a PPP link and the transfer of application data over it require many steps, almost all of which are transparent to the user. Failure to achieve a successful PPP connection can occur during any of these steps. This section describes troubleshooting procedures and debugging information that can make these steps visible to help identify the reason for failure.

These steps can be grouped into two stages:

host-to-host connection

PPP negotiation

Once host-to-host connection is established, the PPP protocol requires that the two hosts negotiate PPP characteristics for the connection before they can exchange application data. Because PPP negotiation is defined by the PPP protocol, it is very similar for all SCO PPP links.

Figure 9-6, ``PPP troubleshooting flowchart'', illustrates a recommended procedure for troubleshooting PPP links. The last step covers the debugging of PPP negotiation for all types of SCO PPP links. The remaining steps cover the debugging of host-to-host connectivity and vary depending on the type of SCO PPP link being debugged. Each box in the figure references a letter from A-G. The list following the figure maps each letter to a particular troubleshooting subsection. Because the functionality verified by the subsections referenced in the lower boxes is dependent on the functionality verified in any boxes above, it is best to perform the troubleshooting steps in the order shown.

Figure 9-6 PPP troubleshooting flowchart

``Logging PPP information''

The debugging procedures for outgoing links made from dedicated serial and automatic dialup endpoints recommend that you use the ping networking command when testing host-to-host connectivity. You can use other networking commands, such as ftp or telnet, but ping is much simpler, and requires less activity for success. If an application such as ftp fails, the problem could be in many places throughout the protocol stack or with the application itself. Because ping uses icmp, it relies only on the protocol stack up through the IP layer. If ping is successful, the problem is less likely to be with PPP. This is because most of what PPP implements must succeed for ping to succeed. See ping(ADMN) for more information.

NPS Fast Facts

Updated: February 18, 2009

Applies To: Windows Server 2008

In Windows Server� 2008, Network Policy Server (NPS) replaces Internet Authentication Service (IAS).

NPS is:

The Microsoft implementation of the Remote Authentication Dial-In User Service (RADIUS) protocol.
Configurable as a RADIUS server.
Configurable as a RADIUS proxy that forwards connection requests to other RADIUS servers for processing.
A required component of Network Access Protection (NAP). When you deploy NAP, NPS functions as a NAP health policy server.
Configurable to perform all three functions (RADIUS server, RADIUS proxy, NAP health policy server) at the same time.
Compatible with user account databases in Active Directory Domain Services (AD DS).

Windows Server 2008 editions and NPS

NPS provides different functionality depending on the edition of Windows Server 2008 that you install:

Windows Server 2008 Enterprise and Windows Server 2008 Datacenter. These server editions include NPS. With NPS in Windows Server 2008 Enterprise and Windows Server 2008 Datacenter, you can configure an unlimited number of RADIUS clients and remote RADIUS server groups. In addition, you can configure a group of RADIUS clients by specifying an IP address range.
Windows Server 2008 Standard. This server edition includes NPS. With NPS in Windows Server 2008 Standard, you can configure a maximum of 50 RADIUS clients and a maximum of two remote RADIUS server groups. You can define a RADIUS client by using a fully qualified domain name or an IP address, but you cannot define groups of RADIUS clients by specifying an IP address range. If the fully qualified domain name of a RADIUS client resolves to multiple IP addresses, the NPS server uses the first IP address returned in the Domain Name System (DNS) query.
Windows Web Server 2008. This server edition does not include NPS.

For more information, see Windows Server 2008 Overview of Editions at http://go.microsoft.com/fwlink/?LinkId=111845.

Upgrade from Windows Server 2003

You can upgrade a server running Windows Server 2003 and IAS to Windows Server 2008 and NPS. During the upgrade process, the server configuration is preserved, including the RADIUS client, connection request policy, accounting, and remote access policy configurations. In NPS, however, remote access policies are renamed to network policies.

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In addition, you can export the configuration of an IAS server in Windows Server 2003, and then import the configuration to an NPS server in Windows Server 2008 by following the instructions in the following article:

NPS servers in Windows Server 2008 systems cannot import configuration settings that were exported from IAS servers in Windows Server 2003 systems

NPS as a role service

NPS is a role service of the Network Policy and Access Services (NPAS) server role. Other role services of NPAS are the Routing and Remote Access service, Health Registration Authority (HRA), and Host Credential Authorization Protocol (HCAP). For information about how to install NPS, see the NPS Operations Guide.

NPS server administration

After you install NPS, you can administer NPS servers:

Locally, by using the NPS Microsoft Management Console (MMC) snap-in, the static NPS console in Administrative Tools, or the network shell (Netsh) commands for NPS.
From a remote NPS server, by using the NPS MMC snap-in, the Netsh commands for NPS, or Remote Desktop Connection.
From a remote workstation, by using Remote Desktop Connection.

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Troubleshooting PPP

Windows Server 2008 editions and NPS

Upgrade from Windows Server 2003

NPS as a role service

NPS server administration