Override this setting in the SonicWALL by going to Security Services - Gateway Anti-Virus - and click "Configure Gateway AV Settings". Check "Enable FTP 'REST' requests with Gateway AV" and click on "OK".
BackupEDGE utilizes the FTP "REST" command to perform Instant File Restore. THis command allows an archive segment to be opened at the exact block where a file begins.
By default, some Firewall/UTMs (Unified Threat Management Systems) Block the FTP "REST" command. This must enabled.
Other firewall appliances may have similar options. Please consult your User's Guide.
On modern Sonicwall firmware, go into the Security Services, Gateway Anti-Virus menu, and click on Configure Gateway AV Settings. Make sure Enable FTP .REST. requests with Gateway AV is checked, and click Ok.
On legacy Sonicwall firmware, you must log in to the Sonicwall, then manually change the URL from the home page URL (usually main.html) to "diag.html". Find the 'Enable FTP 'REST' requests with Gateway AV' checkbox and enable it, then save the settings.