On Monday, all company employees report being unable to connect to the corporate wireless
network, which uses 802.1x with PEAP. A technician verifies that no configuration changes were
made to the wireless network and its supporting infrastructure, and that there are no outages.
Which of the following is the MOST likely cause for this issue?

A.
Too many incorrect authentication attempts have caused users to be temporarily disabled.

B.
The DNS server is overwhelmed with connections and is unable to respond to queries.

C.
The company IDS detected a wireless attack and disabled the wireless network.

D.
The Remote Authentication Dial-In User Service server certificate has expired.

Explanation:

The question states that the network uses 802.1x with PEAP. The 802.1x authentication server is
typically an EAP-compliant Remote Access Dial-In User Service (RADIUS). A RADIUS server will
be configured with a digital certificate. When a digital certificate is created, an expiration period is
configured by the Certificate Authority (CA). The expiration period is commonly one or two years.
The question states that no configuration changes have been made so it’s likely that the certificate
has expired.