Let's first clear up some terminology used incorrectly. The DL1608/DL806 are not wireless devices. There are only two wired connections available to communicate with the DL's. One is the Ethernet connection next to the power connector and the other is the quasi USB connection also known as the dock. Unlike it's competition the X-Air which has wireless and wired connections.
The best way to deal with the hookup is to start with your normal iPad connection to the router which is the 'wireless' connection between the router and the iPad. Once established, the transition to the wired connection is straight forward.
One must use genuine Apple CCK and Apple USB to Ethernet dongle. I have others but the iPad rejects the connection. A powered USB hub is the only non-Apple exception but a necessary item for the setup to work for the 30 pin connector or if you have a lightning connector the new cable that can provide power to the Ethernet dongle. The iPad is the master and the DL is the slave in the USB connection arrangement.
Using your router's setup program one can readily find the IP address of the DL (it's the one with no description thanks to sloppy programming) or you can look at the i in the iPad setup. Once you have the IP address it is simple to set up a fixed IP address in the MF setup (it however doesn't need to be the same as the one given by the DHCP server as long as it is out of DHCP range). Lease renewal should not change the IP address unless it's been a long time and other devices have been added on your network . You do need to be initially connected via DHCP to set a static IP address or via the dock. Note that the MF setup labels the wired IP's as "wireless". The wired refers to the USB connection only.
Since you are connected at this point with what is referred to as a wireless connection (to the router) the CCK and associated gear can now be plugged in and at this point the iPad setup Wifi connection can be turned off in the iPad setup to switch it to the wired connection. Don't panic as there is a loss of sync temporarily after you plug in the wired gear, it will re-sync to it's previous state. Wifi does however not need to be turned off if the 'wireless' connection is down. Best to keep it on to switch back and forth. The wired sync process will follow quickly. There are times where you need to enter the MF setup to get it to sync (some cleanup work here Mackie) sometimes also select the 'wireless DL1608' select. When initially starting up the default in the setup is offline/demo at which time you need to select 'Wireless DL1608' to get it to sync. Yes static IP addresses work and there is no need for a DHCP server. For convenience you will probably use the DHCP server for your setup anyways. Remember no DHCP server no freebee IP addresses given out.
If someone has the Lightning connector it would be helpful to check this with that setup. I will not go there.
My advise is to set it up before a gig if you have more than one iPad, that way you are ready for control. So far I have not had any communications failures down to battery warnings. Please remember that the iPad needs to be charged to last through the gig since it is not being charged while in use. Luck has it that I had to buy the worst iPad ever made the iPad 3. I thought that with 100 Mbps (wired) vs. 54 Mbps (Wifi) I would see a difference in GUI response time,unfortunately not, it's all a GUI problem.
Cheers
P.S. Thanks for all that helpful write-up BenO and Co.