I'm having a weird problem on my Forefront TMG firewall. When I activate my Site-to-Site VPN from the office (178.xxx.x59.130) to the External Interface (178.xxx.x56.4) of my Forefront TMG machine I cannot access the external interface anymore. We work with Outlook Anywhere and thats bound to the external interface of the TMG. I can ping and access the internal devices behind the Forefront TMG server but when I try to access the IP on the external interface it doesn't respond. When I disable the Network "Site-to-Site Branch VPN" the connection is restored.
Am I doing something wrong with routing or is this by design?