This solution applies to all Barracuda Web Application Firewalls.
To make SharePoint accessible using a proxy IP (VIP) on the Barracuda Web Application Firewall, you will have to create an Alternate Access Mapping on SharePoint.This is not necessary when the application is live and DNS is pointing to the VIP.
This can be done on the Central Administration > Operations > Alternate Access Mapping.
Without this, SharePoint redirects incoming requests to the default access for all incoming requests. The subsequent requests from the client bypass the VIP and go directly via the DNS.
Once you are done testing, you can also modify your DNS to associate the original SharePoint domain name with the VIP.
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