Comment 6 for bug 1178273

In my tests the DHCP agent correctly handles the Subnet change and calls the reload_allocations method of the DHCP driver. In the default linux.dhcp driver, reload_allocations results in the dnsmasq config being completey regenerated, and the DNSMASQ process being sent a HUP signal.

Though the quantum python client does not support setting the gateway_ip to null, Horizon does and actually has a checkbox for unsetting the gateway_ip. Horizon returning the quantumError is how i discovered this bug in the first place.

The patch was based on the logic from the subnet_create() method, which only calls the _validate_gw_out_of_pools() method if gateway_ip is not None.

With all this said, I am of course more then happy for others with greater experience with Quantum and its components to make suggestions.