Switching from DHCP on WAN to Static IP on WAN

[phil.davis]

I am getting a remote site setup. The pfSense is behind an ADSL router (please don't ask about putting the ADSL router in bridge mode, double NAT…). Currently pfSense WAN gets an IP address by DHCP from the ADSL router.
ADSL router LAN side is 10.49.153.250/24 - so pfSense WAN gets 10.49.153.n with gateway 10.49.153.250

Now I want to give pfSense WAN a static IP, so I go to Interfaces WAN, change from DHCP to Static then try to add a Gateway.
Trouble is, I need to use 10.49.153.250 as the gateway, but it tells me that is already in use. Well it is the gateway given by DHCP. But when I press "save" that DHCP gateway will be taken down, and I need my new static gateway to come up. Catch-22!!!

I am doing this remotely across OpenVPN. So I need a 1-step process where I can press save, get a coffee, the OpenVPN site-2-site will come back up, and I can continue on configuring.

Any good ideas?

[jimp]

Re-run the setup wizard and use the static IP instead of DHCP there. :-)