Adding new nodes to HA cluster

i have it on 11.2.1 now, and the basic set up is more or less complete. im however faced with a dilemma in terms of not having a proper management lan to sync on, so previously we were able to set this to run on the internal one, which is fair enough. just waiting for my colleague to get back to on how to set the internal interface up to be used for device trust and syncing, and hopefully i wont have to spend the entire weekend in the data center crying:p