I recently found that my DHCP leasing on OVH was unreliable. The address worked at one point, but after a few months/reboots I found that the instance could not longer obtain a lease. After a few attempts to release/renew, I decided to set a static IP.

The General Administration page has general information about setting this. The IP from your OVH control panel for the specific server is needed. From that information the routing gateway can be determined.

The gateway is the same as the IP of the server with the last octet replaced with 254. If the IP is 10.2.3.4, the gateway is 10.2.3.254. To set this on the host:

ipadm create-addr -T static -a $SERVER_IP/32 ixgbe0/v4
route -p add default $GATEWAY_IP