For as long as I've been using a DHCP server on Linux or even FreeBSD (all come from ISC if I recall correctly), it seems that it just doesn't know what to do with DHCP requests when the Internet goes down. It doesn't matter if the gateway is on the same machine or a different router, or if the router keeps working but the Internet has been disconnected, the DHCP server simply stops assigning IP addresses.
This is highly disruptive to our office, where we have workstations that need to connect to our internal customer database, even when we're offline. Never mind what happens to our Cisco IP phones when they can't get their DHCP leases. Sure, we can't make any calls through our SIP trunk when we have no Internet, but the phones should at least connect to the PBX.
Is there a fix for this problem, or is that "just how the DHCP server works"?