WebDAV over VPN

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If anyone can help me with my problem it would be greatly appreciated..

 

I'm pretty new to VPN technology and I'm trying to set home basic home access for school owned laptops issued to staff, and iPad WebDAV access externally via RRAS + PPTP VPN.

 

I've got most of it working tickety boo, everything works perfect from the Windows clients.

iPad clients do connect and they can access intranet sites etc, but cannot access any WebDAV shares by hostname or IP even though they can be pinged. The WebDAV works internally with exactly the same settings

 

Does anyone have any idea what might be causing this? The frustration is driving me insane!