The Network Allocation Wizard is used to automatically add a block based on a mask length, location (you can think of this as a region), and optionally by owner. To access the wizard click 'Allocation Wizard' link on the leftmost frame of your NorthStar window. When presented with the form select the size block you need, the location the block is needed in, and optionally the owner that the new networks supernet must be. The wizard will then search your tree and pick what it thinks is the best block and pass this information on to the new network function. From this point you add the network just like any other, however, you obviously do not need to manually fill in a network and mask length.
The Allocation wizard picks a block using the following logic:
Select the blocks in the system that are in the Location specified, have a status type of 'Allocated' and optionally are owner by the specified Owner.
Find all possible blocks under the blocks found in step 1 with a mask length equal to the one specified
Find all blocks in step 2 that are not currently in the system
Find all blocks in step 3 that have a supernet which has a status of 'Allocated'
Rank each block from step 4 by seeing how many nets exist under the same supernet with the same mask length. This process helps to group allocations by size within blocks.
Return the block with the lowest network number, the highest ranking, and the highest priority
As you can tell the process is fairly involved, but despite it's complexity the Allocation Wizard is fairly well optimized and can find blocks with a good amount of speed.