[hammop1]

Hmm, I CAN add a new site when coming from the internal network. How do I configure the gateway to listen on all interfaces? I don't remember having to do that before, and I can't see where to configure it.

Also, I don't know if this is relevant, but when I go to the Check Point gateway's properties, General tab, and click Get Address it returns the address of an internal adapter, not the external one (this is different behaviour to another Check Point gateway I have elsewhere, which is why I mention it). In the Topology tab, the interfaces are correctly configured for External or Internal.

Thanks again for the suggestions. I shall look into the userc.c idea.