You should consider the following restrictions when resizing blocks and networks:
- The new object cannot exceed the address space of its parent object.
- The resized object must contain some of its previous address space.
- Resized objects must contain at least three addresses to accommodate the network address, the broadcast address, and one assignable address.
- If a child object is no longer covered by the range of the resized object, the child object becomes a sibling object to the newly resized object. The child object must be completely covered or uncovered by the newly resized object or an error appears.
- If an adjacent block is completely covered by a resized block, a confirmation page appears and you need to confirm that you want the adjacent block to become a child of the resized block. The adjacent block must either be entirely covered or not covered by the resized block.
- Resizing a network that results in abandoned addresses isn't permitted as addresses can't be child objects of a block.
- Networks cannot be resized to include a sibling object; networks can only be resized to include unallocated space.
To resize, split, or move an IPv4 block: