I have my 722 hooked up to a router using dd-wrt. I use the "Services" tab to set Static (Leases) IP addresses in the .0.x range to all my gear and then set the DHCP to .100.x range for 5 slots or just turn it off. When you set the Static IPs you have to use the MAC address (00:00:00:00:00:00) of each particular device to do it, so it locks the device and the IP address together. When I power cycle or update the dd-wrt firmware my 722 looses the IP lock and pressing the "Reset Connection" in Menu-6-1-9-2, it takes a couple seconds, it will regain the IP address that you assign to it. It also will do it on its own eventually if you leave it. You can find your DVRs MAC address in the panel at Menu-6-1-9-2. It'll be the green one listed as Ethernet MAC:.
I use this process to lock in IP addresses for my main computer for remote access and this allows for a device that will not allow a static IP to be set in it to function as if it did. I have had this set up for a long time with no issues.
Hope this helps . . .
. . . sf