Windows 7 / Networking

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Troubleshooting Password-Based Validation

Troubleshooting password validation with PEAP-MS-CHAP v2 authentication consists of verifying the wireless client's user name and password credentials and the computer certificates of the NPS servers.

Validating the Wireless Client's Credentials

When you are using PEAP-MS-CHAP v2 for authentication, the name and password as sent by the wireless client must match the credentials of a valid account. The successful validation of the MS-CHAP v2 credentials by the NPS server depends on the following:

• The domain portion of the name corresponds to a domain that is either the domain of the NPS server or a domain that has a two-way trust with the domain of the NPS server.
• The account portion of the name corresponds to a valid account in the domain.
• The password is the correct password for the account.

To verify user account credentials, have the user of the wireless client log on to his or her domain using a computer that is already connected to the network, such as with an Ethernet connection (if possible). This process demonstrates whether there is a problem with the user's credentials or if the problem lies in the configuration of the authentication infrastructure.

Validating the NPS Server's Certificate

For the wireless client to validate the certificate of the NPS server for PEAP-MS-CHAP v2 authentication, the following must be true for each certificate in the certificate chain sent by the NPS server:

• The current date must be within the validity dates of the certificate: When certificates are issued, they are issued with a valid date range, before which they cannot be used and after which they are considered expired.
• The certificate has a valid digital signature: CAs digitally sign certificates they issue. The wireless client verifies the digital signature of each certificate in the chain, with the exception of the root CA certificate, by obtaining the public key from the certificate's issuing CA and mathematically validating the digital signature.

Additionally, the NPS server computer certificate must have the Server Authentication EKU (OID 1.3.6.1.5.5.7.3.1). To view the EKU for a certificate in the Certificates snap-in, in the contents pane, double-click the certificate, and then on the Details tab, click the Enhanced Key Usage field.

Finally, to trust the certificate chain offered by the NPS server, the wireless client must have the root CA certificate of the issuing CA of the NPS server certificate installed in its Trusted Root Certification Authorities Local Computer store.

For additional requirements for the computer certificate of the NPS server, see the section "Requirements for PKI" in this tutorial.