The MAC IP Anti-Spoof Module for SonicWALL is a great way to protect against the increasingly common spoofing attacks used by modern attackers. However, it may not be necessary to have it enabled for every device and it may actually interfere with some devices on the network, denying them access because it thinks their IP or MAC addresses are spoofed because the SonicWALL has detected them outside the network before, whether from a VPN or otherwise.
Launch your Web browser and log in to your network security appliance using your administrator credentials.
Click the "Network" option from the left menu and select "MAC-IP Anti-Spoof" from the provided sub-menu.
Click the small pencil icon next to the interface you want to disable the MAC-IP Anti-Spoof Module.
Clear the box labelled "Enable - Enable MAC-IP based anti-spoofing."
Click "OK" to save the settings. Log out of your Network Security Appliance before closing your Web browser.