We have a DRG22i in service.
We haven't upgraded it's software but the factory default appears to be to DHCP.
cf : DRG22 which has a factory default fixed IP address in private address space.
Once the DRG22i had DHCP'd it's IP address, we were able to use the browser interface to configure it.
As I say, we didn't upgrade it, but I'm pretty sure one of the configuration pages is to 'Upgrade'
There is a CD that comes with the DRG22i which I gather helps manage large numbers of DRG's. We didn't need to use any of the stuff on the CD to get it working.
The main catch we found when setting up DRG's was the requirement to initiate the phone number with a mandatory password. Then the H323 alias in the DRG has to match the password (or the H323 alias IS the password, whichever way you want to look at it)