Thanks nellie4568. In my use case, I have no control over node A (whereas B and C are mine). I can only sync in read-only mode with A. I can afford having my node B (a desktop) to sync with A. I have no issue my B and C nodes to sync in Read-Only mode to each other. The reason I do not want to C to sync with A is that C is a phone and, as I do not mind C to sync with B, I do not, however, want my phone ( C ) to sync constantly with A over internet considering the data to be synced in this case is over 20 GB.