Going to install tonight, have some questions

Hello, I am a new user here and I will be doing the Multi-db conversion tonight hopefully

But before that I have a few questions, is the script fully compatible with previous versions? I am currently using version 1.5.1

Also, what does the DC mean? Also, is the LAN_HOST ip needed? I have my own dedicated box, should I just leave it to be

I will be splitting the db to 256 databases, I have around 3-4k blogs at around 28k tables. I should be ok with this I guess.

Thanks for the help