Microsoft Challenge Handshake Authentication Protocol version 2 (MS-CHAPv2) is a secure authentication protocol used by Virtual Private Network (VPN) connections to authenticate the user. It is often used in corporate environments to provide secure remote access to the corporate network.
MS-CHAPv2 is an improved version of the original MS-CHAP protocol, which is an extension of the CHAP (Challenge Handshake Authentication Protocol) protocol. MS-CHAPv2 is an industry-standard protocol and is supported by most operating systems, including Windows, Mac OS X, and Linux.
In order to use MS-CHAPv2, the user must have a valid username and password. The authentication process begins when the user connects to the VPN server. The server will then send a challenge, which the user must then respond to with the correct response. The response is calculated using the user's username, password, and a random number generated by the server.
If the user's response is correct, the server will reply with a success message, and the user will be granted access to the VPN. If the response is incorrect, the server will respond with an error message and the user will be denied access.
In some cases, you may need to force MS-CHAPv2 as the authentication protocol for a VPN connection. This can be done by modifying the connecting client's settings.
On Windows, you can do this by opening the Network and Sharing Center, clicking Change Adapter Settings, right-clicking the connection you want to modify, and selecting Properties. In the Security tab, select Advanced Settings and check the box labeled \Require MS-CHAPv2 protocol for authentication.\
For Mac OS X, open the Network System Preferences, click Advanced, select the VPN tab, and select MS-CHAPv2 from the Authentication drop-down list.
On Linux, open the Network Connections window and select the desired connection. Then click the Edit button, select the Security tab, and select MS-CHAPv2 from the Authentication drop-down list.
Once you have made the changes, attempt to connect to the VPN and the connection should now use MS-CHAPv2 as the authentication protocol.
Forcing MS-CHAPv2 as the authentication protocol for a VPN connection is a simple process and can be a useful security measure for corporate networks. It is important to note, however, that MS-CHAPv2 is an older protocol and is not considered as secure as more modern protocols such as EAP-TLS or PEAP.